GMC Repair: 1973 chevy c10 pick up conversion, buick roadmaster, 1992 buick roadmaster

Question
hello there i know you only answer questions about cars from 79 on .the problem im having is with a 1992 buick roadmaster motor and Trans the 5.7 i put them into my 73 pick up.not so much the Trans but the motor is what im having trouble with.ive swapted motors before,but this is the first time im doing a complete change over. the original motor i pulled out of the truck was carburetored 350.now going to fuel injected.  when i pulled the motor out of the buick it ran fine . when i finished putting it into the truck it will not run.i have spark i have fuel .i have compression. when i turn the key you get the initial burst from the injectors  but once you start cranking the motor the injectors stop .ive changed the ECM and still nothing ..as far as i know i have all grounds in place.is there maybe a security system that i don't know about built into the wire harness?ive been working on this for 6 months its all together and now i cant get it started.please any info would help me greatly.

thank you for your time enclosed is my number 908-461-3578 if you feel you more info  please feel free to call. im not a machanic but i am in need of some help from a pro.and thank you again for your time.

                        luis

Answer
Hi
quick questions
Did the loaner car have a "chip" in the key?
IF SO it sure does sound like a Passkey or VATS problem.
It'll be two VERY small whit wires wrapped in ORANGE shrink wrap coming from the column key cylinder and there was a connector about 8 inches to the RIGHT (passenger side) of where the column was. Two REALLY small white wires.
Do you have the original Raodmaster key?
Please follow post back
Check mark the Private box also.

Pawl