87 camaro

My friend and me have been working on a car of his. He had two camaros sitting around, one was a 91 3.1 automatic and the other was a 87 2.8 5 speed and we got playing around with them one day and took both the motors out. the 87 had a blown motor and the 91 had a bad tranny. we put the 3.1 in the 87 and after we got it hook back up we tried to turn the key and nothing... is there a computer problem? and the wires on the starter selenoid... where does each of the wires go? one goes to the starter, the other to the positive cable, and the small ones go on which of the smaller posts... the one on the inside or the outside. Also, we got some of the pins to fix the door where it hangs really low, could anyone tell me a good method of replacing them? im not a mechanic, we are kind of just doing this for fun. any advice at all... and i mean at all would be appriciated. We are trying to get this car together so we can ride to work in a decent car without paying 100 bucks a week for gas. Please help us!

You are going to have a mismatched engine/harness there. There are some differences in those 2 engines. But if you can get the ECM from the 91 and harness (don't forget VATS too) you should be able to get it hooked up and running.
The starter wires go...large wire to the big stud wire on the solenoid and all of the smaller wires should go to the little stud closest to the engine.
for the doors you need to support the door with a jack with a 2x4 between it and the door. remove the side kick panel by the floor. While the door is supported look under the top of the hinge where the pin sticks through. you should see a metal clip around the pin...take it off. You'll also need to remove the spring from the door, be careful it is a very powerful little spring. Then hammer the pin up and out. with the pin out, remove the body side of the hinge (there are bolts/ nuts where the kick panel was).You'll have to move the door up and around to get the hinge out and back in) Pay attention the where and how the bushings in the hinges are located. Remove the bushings and install new ones. Reinstall the hinge and line up the pin holes. Hammer the new pin down in all the way so the knurled part under the head is down in the upper hinge flange. reinstall the spring (there is a tool for doing this)

Alright I think we can handle all of that, but what are VATS? Ive never heard of that before. Thanks.

Alright I think we can handle all of that, but what are VATS? Ive never heard of that before. Thanks.
Vehicle Anti Theft System. It is programmed into the ECM on 89+ Camaro/Firebirds. There is a little resistor chip in the ignition key that the ignition lock "reads". If the key's resistance doesn't match what the VATS module thinks it should be...The ECM won't let the starter engage.

So... I would have to switch the ignitions on them? How would I go about that? Are they the same, because this one doesnt have an air bag. Thanks for all the help.