My mildly modded 350 crate W/Rochester tripower has run perfectly since the first time it was fired up - 2 years running so far. Most of of the credit goes to Ron at..,

http://www.chevytripower.com/complete.shtml

http://i36.photobucket.com/albums/e22/riverwork/Public%20stuff/Truck%20Parts/Fintrk9.jpg

...it was bolt on and when fired up, just a couple minor adjustments on the center carb. I would call Ron & possibly send your carbs to him. They can be flakey if the outer (dumpers) are not done right to begin with. When done correctly, Rochester trips are a reliable, old school road trip that gets lots of looks & conversation at shows.