No experience with the repops, but the old original 300 HP 327 ram's horn manifolds with the 2 1/2" pipes were some of the best I ever ran on my dyno. Other than a tuned header with equal-length pipes for all cylinders, they gave the best torque output over a wide range of RPM. Even regular unequal-length tube headers couldn't match their performance.
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!