That's the engine program GM used to call "Target Master". New, not rebuilt engines, sold through their dealer parts departments, and priced competitively with aftermarket rebuilders. I used to install quite a few of them, and even used them as the basic core for certain race engines I built for budget minded competitors. Upgrading things like camshafts, and intake and exhaust components made them pretty comprtitive for the guys who couldn't afford a $15K full competition build. (30 years ago- - - -today's prices are a LOT higher!)
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!