will it fit
 

I have a 95 Buick Skylark that I loaned to my son-in-law and he drove it for a few days just fine bit the check oil came on and instead of stopping and checking the oil he kept on driving until the engine shut down for lack of oil he let it sit for an hour it then started and he kept driving and got it to his house a called and said the car is making a funny noise and he doesn't want it anymore it has a 3100 motor in it and it still runs but the rod bearings are toast would it be possible to put a 3.8 liter or should I stick with the 3100. it was a nice car that got good mileage while I am at it I might as well fix the transmission that won't shift.