1994 Other GMC Models will not start

Hey I have gmc top kick lo pro with a big block v8 otherwise known as a uhaul. My dad had the engine rebuilt just recently but the guys who put it together didnt replace stuff you would normally replace during an engine overhaul. It was running rough and I moved the distributor to straighten it out. But he had me replace the distributor, the fuel injectors, the coil, the map sensor, the fuel filter and the oil pressure sensor. I went to start it and it started to fire and immediatley stopped. I checked for spark and there is spark getting to the spark plugs. The fuel injectors will spray once when turning the engine over and then its like they spit tiny amounts of fuel out. Did I not do something right with the injectors. Fuel is getting to them I checked