340 Build.

Ran a 70 340 swinger x heads 10.5 comp. stock pistons, weiand dual plane ,cheapo 232-242 112 hyd cam and also 242-242 508 paw cam 750 vs carb 3000 conv. 4.33 rear. Ran 12.0 with 232 cam, 12.20 with paw in very good air ,12.0-12.40 in summer .Nothing special should have no problem with a street solid roller to get where you want to be.
Did you do new pushrods/springs?