Backfiring out carb and wont run right

You need to make sure your timing is right, it'll prob want 16* or more initial, and prob need to modify your distributor advance,, there are lots of threads on that,, and it basically sounds like your Accelerator pump is weak,, here's how to adjust it..

http://forums.holley.com/entry.php?428-How-To-Cure-Carburetor-Stumble

hope it helps