sound like your timing has wandered a bit,,,also make sure there are no vaccume leaks on that motor,,,,with a lumpy cam,, your motor will generate less vaccume anyway,,so a little leak will cause big problems.
what type of coil / distributor are you using??,,,maybee swap out the coil from a known good running engine,,,and see if this changes anything.
You may want to check to see if your distributor is advancing when you rev it up,,,without advance,,it's gonna run like crap.