Lots of GMCs were repowered with Chev. The Chev is about 1 1/2" shorter. A plate on the front mount will fix that. The rear will require no changes. Many Chevs drop the exhaust out the rear while GMC drops it out the center. However, I agree that you should look for a GMC. Even a 228 will be far superior. A 248 or larger is even nicer.