1992 Oldsmobile 3.4 to 3.1

We have a 1992 Olds Cutlass Supreme, it has a 3.4 in it and we would like to change it to a 3.1. We have had two other Oldsmobiles with 3.1 and they were much more reliable than our 3.4. Since it is my car my husband said he would change the motor to a 1990 model 3.1 that we already have out of a car that was wrecked. It has 80,000 miles on it. He wants to know if it can be changed and if so what needs to be done, such as change the wiring harness, computer etc. Thanks so much.