I finished my swap on my blazer everything is hooked up it's just backfiring and not completely starting I keep going over the timing but it doesn't seem to change I used the crank sensor for my V6 vortec cuz it is the same part number any suggestions should I try using starting fluid maybe the gas is not getting up to the carburetor where the throttle body I meant to say and with that should I get rid of my spider injection and use the old system

 

Did you change the ECM when you did the swap? How about the distributor, was it removed and replaced?