Before you upgrade the carb, spend some quality time with the ignition. The stock advances are not conducive to high performance. They are too slow in coming in, and advance too far to keep the power levels where you want them. I would at minimum get the MP light spring pgk, and a timing tape. Install one light in place of the one stiff one in the dist already. The next step, you need to see on the plate the weights slide in (this has to be removed to acces the springs anyway...). It will be stamped with the number of degrees advance it provides. If it's more than 15° then it will need to be welded up. The idea is, if it's stamped "22", you will want to block off the outside 1/3 of each slot. (22-15=7, so you weld up the outer 1/3, and now it's a 15° plate) You need to make sure the slots are filed smooth, so there are no burrs, and you'll want to be sure the center of the pin on each weight contacts the welded spot correctly. So the amoutnyou block out is really only 1/3 of the slot's travel. Then, reassemble the dist., and reinstall it. Set the initial timing to 18°, and the total should now be 33° and it shoudl come all "in" by 3K rpm, leaving the fvaccum advance disconnected, and the line plugged at the carb. Then, plug the line back on the vaccum pod. Most have an allen wrench accessable adjustment screw inside the nipple where the vaccum line plugs on. You can either add or remove preload on the diaphram to quicken or delay the pod's advancing. Counter clockwise adds preload (delays the pod) and clockwise removes preload (quickens the application of the vaccum pod). Popping or surging means you need to delay it a little more. I start with that adjument set for quickest application (no preload), and test drive. If it pops when floored, go 2 turns of the wrench, then test drive again. No pop but a light throttle surge, at cruise, add another 2 turns. When the surge is gone, it's done. When that's done, you can tell if the carb is too small. My guess is, it wont feel as sluggish, and it might be ok. If I were building this engine, and your rear gears are lower (numerically higher) then 3.23s, I'd run a larger carb. The 750 Thunder AVS would be my first choice.
