I helped a Tennessee forum member who used to post a lot a few years ago assemble an oddball GMC engine, a 256 cubic inch that supposedly was used in WW II Canadian military vehicles. It had a set of those stamped steel rockers. The 256 had a 248 crankshaft and a 270 bore. Those are extremely rare engines, and it was not original to the truck he was restoring, a 1951 long bed pickup that had belonged to his father.
Jerry