1998 Dodge Dakota crank, so start, cuts spark and fuel
 

So... It was a 1998 Dakota, auto, v6. The motor siezed, so my friend asked me to help with a V8 swap. He got the motor from a 1997 ram 1500 pickup that ran. We used the v6 harness and added the two injectors, as well as swapped to the correct oil pan.
When the majority of the plumbing and wiring was done, we fired the motor in the truck to test it before it was 100% complete. It started right away and ran for about 30 seconds till it shut off. When we tried to restart it it fires right away but something cuts spark and fuel the same second the motor fires.
We tried a few different pcms, as well as swapped crank sensors as well as the sensor in the distributor. It's getting to the point where I do t know what to do next. I'm still going to school so I can't spend a lot of time in the shop working on it, and he needs a vehicle to drive asap. Any ideas would be great.