Tom,
On this topic I definitely agree with Gary R. A 350 does not need anything more than a 650cfm on it. I find that a 600 is a good carb. As for the brand, it really depends on what you prefer. If you want simplicity, then Holley is your best bet, due to the fact that it has the least amount of parts in it, and it is easiest to rebuild. However, it is the biggest pain in the ass because you constantly have to tune the damn thing if you decide to romp on it and race around. A Rochester Quadrajunk, on the other hand, is a great carb, WHEN IT'S PUT TOGETHER CORRECTLY. Once you tune it, you can walk away and forget about it. The problem is that it has about 1,000 parts in it, and rebuilding one is a headache and a half; I know this from first hand experience. I have a 795cfm on my 79 L-82 Vette. I know what I said about a smaller carb on a 350, but it came from the factory like that...why I still don't know. I hear that Edelbrock makes a good repro of the Q-Jet, but I have never tried it. The choice is really yours. Good luck on your decision.