The only thing better than a GMC 270 is a GMC 302. Chevy can't hold a candle to a good GMC. The downside is parts availability and price. You could probably build at least two 261's for the cost of building one 270. Back in the 1950's 270's were a dime a dozen, mostly WW II surplus military engines. Round track racers and Bonneville speed record contenders snapped them up pretty quickly. Now they're very scarce and expensive to build.
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!