" I would caution you on installing a GMC 302. I don't have any personal experience, but have been told that the block is longer and isn't a simple swap out."
The GMC 302 is the same physical size as the 228 in the truck now and is a direct bolt in replacement with no modification*. All GMC engines in the series are longer than Chevrolet engines of the same era. Modification is required to put one in a Chevy.
*If the later engine uses side mounts you will need to swap the timing cover plate from an earlier engine.
