From this chart, it appears that the last year for a 2-letter suffix code was 1969, but that one doesn't show.

https://novaresource.org/codes.htm

By 1970, it also appears that the 230 6 cylinder engine was not produced- - - -250 only listed from 1970-up. I also wonder if the site I found was only showing passenger cars, not truck applications?
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!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!