Duster 340 not a muscle car...

It didn't matter what rating chevys had. They were all talk, no walk. I saw them get run down all the time. 396 chevelle's especially. Dogs, 350 chevy 350HP? 340 Dusters chewed them up all the time. 340's In reality were much higher in the HP than 275. Chevys were hoity toity guy cars, driven by guys that had no idea how cars worked.
This of course is the opinion of an old 60's Mopar guy.