Can't help with the suffix code, but the dished pistons definitely make it a 250. Both engines have the same bore- - - -3 7/8", but the 250 uses the dished piston to keep the compression ratio the same as the shorter stroke 230 engine. Flat top pistons for a 307 V8 are a drop-in fit for a 250, BTW, and they give a pretty good compression boost.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
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