AFAIK, the GMC mill is about 1-3/4" longer than the Chev. six.
Since the GMC engine compartment is longer; you should not encounter any clearance problems with regard to the water pump and fan clearing the radiator.
Engine mounting is another thing.........you may have to fabricate a mount; since the GMC frame is different than a Chevy (they weren't "homogenized" until 1967).
I vote for a ring and bearing job for your 228 or find a 248,270 or 302 to bolt in.
Then you would have a "drop-in" situation
.
Try
Egge parts. They will send you a catalog and a
free quote on the parts you need to save your 228.
