I would stay all original and have the AVS rebuilt as well. I had a 71 Chry 300 4dr HT that was all stock with the 440 with the AVS carb and I can tell you its the only car I have ever driven that scared me. Not because of its stability at high speeds but that it would go as fast as it did. I have sent its speedometer out of the dash many times and anything Brand X after 70 mi per hr just as well slow down and stop because they couldn't hang with it. It really shocked many people. If you want to get the car to have better low end I would change the rear end gearing. My chry was 2.76's and you could switch to 3.23's or even 3.55's and it would drive fine and be a screamer taking off if that's what your after.