Look at the pictures on the 6066gmc page. The 230 and 250 look identical. The 292 has taller (6") side covers and the fuel pump is rear of the motor mount. Compare the pictures. It should be easy to eliminate or confirm the 292. If it is a 292 then you are a lucky guy. congrats!
As Tim suggested post the stamped serial number found on the little flat boss rear of the distributor. That and the casting number 348675 should pinpoint it. The A25 is a casting date: Jan 2 65...


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