My '52 GMC 228 has a 2136477 head with a casting date of 6/14/52. It has domed (original I think, at least the bore is still standard) pistons. The 1939-54 GMC Master Parts Book calls for one set of pistons for 1939-52 228 engines with 6.75:1 compression ratio (domed) and a different set of pistons for 1953 228 engines with 8:1 compression ratio (flat).

Pictures are of my #5 piston and combustion chamber. The exhaust valve was badly burned. Had a machine shop do a valve job, I re-installed the head and 40,000 miles later it is still running strong (as 90 hp will run).
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Last edited by Bill Hanlon; 11/16/2022 4:19 PM. Reason: additional info
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12
'52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.