Transmission Swap - FMX, C6, or...?

Just got the original I6/C4 out of my Torino. I have a mostly stock 351C CJ ready to go, but need a transmission. I do have a FMX transmission that could work, but can't find any shops willing to rebuild it because of parts availability. 

What are my best options here? Also keeping in mind clearance for my headers. It's a 1973 Torino. Thinking of the possibility of going with a built C4, or maybe even AOD or 4R70W, but I do have 3.00 gears in back so I don't really need overdrive. Thanks in advance.

Inkara1 wrote: My big question is if there exists a header for a 351C with 2V heads and a C6. Or will 4V headers work with 2V heads? (I don't think so but I could be wrong.)

there's not enough material around the 2V exhaust port to seal a 4V header on US heads but they say the Aus 302C heads will seal the 4V header, there's a little more meat on them. cheap work-around if you have a set of 4V headers what i did was fabricobble myself a set of adapter plates. i traced around the outside of a 4V gasket then overlaid a 2V gasket centered on the bolt holes and traced the inside. it verked!

in the early days of the 351C before Edelbrock released the F351 #2750, sourcing a take-off factory cast iron 4V manifold and fitting it to the 2V engine was fairly popular. an old magazine article claimed the swap was good for 30-35 hp. whether or not you'd notice any difference i can't say, but in Cali i'd go with the Airgap manifold rather than the std performer. a lot of are disappointed by the smaller than port sized runners in the std performer, some guys make the alloy swap just for the weight savings alone. if keeping it stock appearing is important an Aus 302C manifold is an option (they have the 2V port size internally) but they're not extremely available and the choke stove piece (different from the US counterpart) is harder to find than the manifold itself. FYI there are at least 3 different 302C intakes, 2 spreadbores and a square flange that would suit your carb.