intake backfire. help please.

[Foreverenvyed]

okay so i recently just replaced the shortblock from my 347 to a stock 302. the car ran great before i swapped the shortblock, but now when i try to start the car i have to start it with WOT and it will barely start then when it did it sounded good till about half throttle to full throttle it would start to backfire through the intake. the car is timed to tdc. it has roller rockers that are set correct. 30# injectors with granatelli mass air. ported e7s, proproducts intake, spacer, and throttle body, bbk cold air. stock fuel rails. and now the car wont start at all idk where to start. i know the 30# inj. and mass air are too big now but it wont even start now and would them being too big cause the engine to backfire through the intake. i know its timed to tdc correctly and i pilled the timing cover and the chain was correct too. any information helps. i just dont know. oh yeah the car is a 92 gt

 

[CC'S95GT]

double ck the firing order and timing.or have someone else you trust.
Did you pull the spout when checking the timing? gotta ask.
How old is the harmonic balancer? the old one may have slipped.

 

[Foreverenvyed]

yeah has a new HBalancer new distributor. im just trying to fig. before having to pay someone to come out.