The man asked about his engine and immediately you guys start talking in favor of one he doesn't have. Try sticking to the subject matter boys. His interest is in the eggs and so you start telling him about ham.
I think with over 1300 posts, the OP can figure out what is useful information on his own. The fact of the matter is there are more parts available for a 270 or 302 motor, and those motors make more power than a 228. If you look at the HP a 228 makes compared with the HP of the 270 or 302, you will find the 302 to give the most HP for the least amount of money.
If it costs $3000 to rebuild any of these motors to stock specs,
The 302 with 160 HP will cost $18.75 each HP.
The 270 with 140 hp will cost $21.43/hp
and the 228 with about 110 hp will cost $27.27/HP
True this does not take into consideration the cost of getting the other motors to rebuild, and does not factor in the type of build. Perhaps the 228 is being used to do a numbers correct restoration.
I believe the cost/hp to be an important factor in rebuilding an engine.
There are plenty of companies out there that will make custom pistons for the 270 and 302 motors such as Venolia and Arias. I don't know if they also make custom pistons for the 228. Finding parts for the gmc engines can sometimes be frustrating. The above referenced post(s) were not intended to be snotty.