My car is an 85 TA T5 ex-LG4. I swapped it for a 86 350 that's built. I don't have any computer controls. The engine is using the original starter, alt and battery and has a edelbrock 750 and hypertech distibutor. The car will start but die right when the key is turned to the on position. There is also no lights or any gauges except when the key is in the cranking position. I tryed another alt and battery but the same thing happened. All the holes that aren't used on the carb or intake are plugged also.

 

You have a wiring problem. First guess, coil is hooked up wrong. Second guess, wrong wire is hooked up to power stuff when the key is on (like lights, gauges, coil, etc.), its hooked up to a switched source instead that only has power during cranking. I know how to do that feat on a Ford, but not a Chevy. I'm sure you could though, and maybe thats what it is.

 

recheck your wiring... also check for blown fuses..

wiring is the least favorite thing when i work on cars..