Any ideas? 

E) Check and verify that the power valves diaphragms aren't leaking and/or that they hold a vacuum. F) If you have pin drill bits and a micrometer, verify the IFR(Idle feed Restrictor) orifice size in the primary metering block, Holley tends to size these on the large side. For a 750, they should be in the .033-.035" range. G) Idle air bleeds (outer most "holes" down at the top of the carburetor) aren't blocked with any debris. If the carburetor is a used piece, maybe installing a rebuild kit would be a good idea. Hope this helps.

No matter where I set the float levels, it seems like fuel is just dumping into the carburetor somehow making it very rich at idle and it won't even clean out when you try to raise the RPM.

One thing I did notice though underneath the squirters there is a needle valve shown on each one and they appear to be missing along with the check balls. And there is a note on the rebuild kit that used only in mid '70s or earlier carburetors however that note only applies to the check ball and the weighted check ball and not the needles. Both needles and check balls appear to be missing in this carburetor could that be the cause of the problem? And if so are these needles and check balls universal across all Holley carburetors in size?

The diaphragms that were in it originally were a 3.5 would this caused the problem I'm having?

i think what you're saying is rated 6.5 / 3.5 are the power valves, accelerator pump diaphragms don't have any rating other than the basic size based on the volume of fuel they're capable of moving averaged over 10 strokes. IIRC they're 5cc, 30cc and 50cc. the needle & seat assy's are designated by the size of the orifice opening, AFAIK as long as they're the correct basic style they're interchangeable, the orifice size does not affect fitment or function. no i don't see anything you've mentioned if working properly and in good condition causing the trouble you're having

What's the difference in power valve sizing give me the rich condition?

I also read a post someplace about secondary idle adjustment, I haven't messed with that yet Do you know anything about that?

the power valves are held in the closed position by manifold vacuum. as you're driving and step into the throttle, manifold vacuum drops and the power valve opens as the manifold vacuum drops past it's rating. a 3.5 PV will open as the manifold drops below 3.5Hg, and a 6.5 PV will open as the manifold vac drops past 6.5Hg. the 6.5 PV will open sooner / earlier than the 3.5, i think you have the 3.5 and the 6.5 reversed, 6.5 is the primary and 3.5 is the secondary in a Holley 6709, jets are 652 and 76. some Holley info https://www.mortec.com/carbs.htm" rel="nofollow - https://www.mortec.com/carbs.htm

the secondary idle is usually accessed from the underside of the carb base plate, in most cases it never needs to be adjusted at all. it's not likely to be causing your issue. a quick search of the internet turns up no love for that 6709 at all, they say the metering blocks are the 'reverse idle' type where the idle mix screws actually control air rather than fuel. nothing wrong with that in / of itself other than it's good to know if trying to set the idle mixture! me personally i'd really consider replacing it before $ any more into it. what kind of power / performance level are we talking about?

I went through the750 again very meticulously, 65 pv in primary and 35 in secondary.652 primary main jets and 70 in secondary. I put the Holley regulator on and with all that it won't idle. Running the choke it is between not enough fuel to stumbling rich.

I went out and bought an Edelbrock AVS2 650 and bolted it on and it starts right up idles fine and is pretty smooth. But my uncle swears by the old 750 said it gave double digit mileage and power. I can't help but think I'm leaving some horsepower on the table ! I'm thinking about trying to find a Holley expert to go through the 750 and see if I missed something. At least it runs right now , that's a little progress😉