I asked this question years ago.  Here was some discussion about it. 

Paul

yeah i remember this coming up before possibly other places too, maybe a thread merge to consolidate it all?

what's your build date, and what assy plant? chrome lid or painted? aux air valve or no?

what all this has to do with the air cleaner decal, IDK but it's my way of breaking down the various different engine builds. George Pence created this chart, IDK exactly why he designated each column the way he did or where he got the info to distinguish them as such? FWIW i see some things i'd change but i don't think it amounts to much for the air cleaner decal question

closed chamber / high compression M code production ceased and open chamber / low compression Q code production began mid-1971, i put the change early to mid July.'officially' the entire 1972 model year production was the same open chamber / low compression engine. 1973-74 model years saw a change from flat top pistons to dished pistons and the lowest compression ratio of all 351C's

there's at least 1 guy that takes the Q code and Cobra-Jet monikers very contentiously, IIRC he refuses to accept the 1973-74 as Cobra-jets or i may have that backwards. he's a PITA.

here's a similar run-down by Tom Custom

==============================

The Q code is the Cobra Jet and it is a Cleveland. 
by Tom Custom 
The Q code engine package was introduced in 1971 as a performance version of the 351C. Here are the different versions of the US 351C

1970:
H code 351C-2V, two barrel engine, 9:1 CR, open 2V style heads
M code: 351C-4V four barrel engine, 10.7:1 CR, closed 4V style heads
The M code used a small cam. It was powerful, but not a performance engine. That is, it didn't have any "race" parts. Both engine used positive lock rockers and flat top pistons. 

1971:
H code 351C-2V, two barrel engine, 9:1 CR, open 2V style heads
M code: 351C-4V four barrel engine, 10.5:1 CR, closed 4V style heads
R code: (BOSS351) four barrel engine, 11.7:1 CR, closed 4V style heads with adjustable rockers, forged pistons, high strength rod bolts, crank selected for a minimum hardness, solid lifter cam, large balancer, four bolt mains, dual point ignition, special exhaust manifolds (not that you could tell by the outside), baffled oil pan, aluminum intake and big spread bore carb. This was a serious performance engine package.

1971.5:
Q code: Cobra Jet 4V 9:1 CR four barrel engine. Had special parts like high lift cam (same profile as 428CJ), dual point ignition with 4 speed, larger harmonic balancer, baffled oil pan, four bolt mains, big spread bore carb. This engine used open 4V style heads with positive lock rockers. Lower cost, easy maintenance, regular gas performance engine.

1972:
H code 351C-2V, two barrel engine, 8.5:1 CR (or so), open 2V style heads
Q code: Cobra Jet 4V 8.5:1 CR (or so) four barrel engine. Same as 1971.5
R code: HO four barrel engine, 9.5:1 CR, open 4V style heads with adjustable rockers, forged pistons, high strength rod bolts, crank selected for a minimum hardness, solid lifter cam (slightly different than the Boss), large balancer, four bolt mains, dual point ignition, special exhaust manifolds (not that you could tell by the outside), baffled oil pan, aluminum intake and big spread bore carb. This was a serious performance engine package, and a low compression version of the Boss.

1973:
H code 351C-2V, two barrel engine, 8:1 CR (or so), open 2V style heads
Q code: Cobra Jet 4V 8:1 CR (or so) four barrel engine. Dished pistons, 2V sized valves in the 4V heads. Cam is identical to 1971 except ground 4 degrees retarded. It gets an EGR system. Only 4V Cleveland engine option in 1973/74.

The 1973 Q code used a special air cleaner housing with the usual snorkel on the right side, a second air inlet controlled by a vacuum servo on the left (US driver's) side, and a chrome lid. Transmissions with the CJ were either the Toploader (only close ratio available in 1973) or the C6 with a special smaller diameter, high stall torque converter. Dual points only with 4 speed. All CJ years cam with a cast iron spread bore intake manifold


1974:
Same as 1973. No 4 speed option so no dual points for Q code. Last year for the 351C. In 1975, the taller deck 400 would used with a destroked crank and different pistons to make the 351M. The 400 continued with the 351M until 1980?

i thought about this today, is there a part number on the decal?

this ebay ad shows a number but i can't quite make it out

https://www.ebay.com/itm/393071874082?_ul=IN" rel="nofollow - https://www.ebay.com/itm/393071874082?_ul=IN

If I were to guess, it was the 71 built 1972 models that used the CJ, and once supply was exhausted they switched to the 4V labeled cleaner in late 71 or 72.

On the part number thing. My 98% original 72, built in April, has many of the trim and decorative parts numbered with D3Ox-xxxxx-xx part numbers. I even have trim and interior parts that are clearly stamped with a "rejected" inspection stamping, but were still installed. 

On the CJ vs. HO, McFord might know something, I'll reach out to him. I know he was at one time compiling information to try and determine which 72's had black firewalls vs. body color. 

This is clearly about stock air cleaner labels, but does anyone have idea if any had the rhinoceros figure on them? I think those were all later references by people or aftermarket companies.

I think I'll need a label made to fit my aftermarket 14" open element air cleaner. I know someone that can design any label, but still I haven't hunted somebody to produce an actual sticker. I think mine should have 351C-4V on it, given high compression, plus premium fuel for sure. I'd like to design one with the rhinoceros prominently included. I want one that is similar to OEM designs and colors, but fits the size and shape needed, without various lettering I don't care about(such as no foreign text on it like all modern cars, which all have French).

I also have the black firewall. 

Here is a pic of my 72 H.O. sticker from my 72 R code as a comparison.

yes George Pence's analogy of the 4V hitting it's stride,

one place you don't want to be is in front of a Charging Rhino!

i don't think they stop until they hit something?

South Africa used Charging Rhino decals, i believe they were on the fender in front of the tire

Australia used the Super-Roo decal same location

regarding the M code air cleaners, i'm thinking they had a '4V Premium Fuel' decal?

i don't know for sure i'm makin up now

NO, they didn't have charging rhino's on the decal.

ALL 351C 4V (Q code) torino's/ranchero's/montego and cougars (1974) from 72-74 had the vacuum valve on the drivers side of the air cleaner base.

1974 the lids were painted blue, same as the engine and air cleaner base/snorkle.

The ONLY difference between the chrome lid (1972/1973) and painted lid (1974) is the chrome.  That's it.  Same stamping.