Isn't there a GMC V8 (Pontiac) with 348 cubic inches? It's a downsized version of the Pontiac 370, so the same freeze plugs should work that fit the 370 engine.
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!