Is my engine performing as it should??

I am haveing very similar problems with a 340 j heads port matched purple .450 .455 268/272 670 avenger hp manifolds tti2.5 15.2 1/4 2.2 60 ft 3.23 gear It quit pulling at 5500. so far i found i used a dial back timeing light. bad. it was off. i thought i had 36 total and it was more like 40. I`m going to change plugs corect timeing to 15 initial 36 total. and wile the plugs are out do a compreshion check and give it anouther test. If i forgot anything i would appreciat the help. I did check to make shure the carb is wide open and will do it again.their were times on the street in 1stgear it went up to6200 easily but not that knight.