All GMC engines look similar- - - -228, 248, 270, and 302. There's also a 256, but they're extremely rare- - - -mostly Canadian military engines for that one. The only real way to tell the difference is to look at the stamped number by the distributor, or measure the bore and stroke.
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!