I've dyno-run similar manifolds to 6500-7K with very good results. That's a pretty conservative speed rating! On the "cheater" engines we ran on the 1/2 mile round track, the ignition would crap out long before the carburetion got marginal. We were running 355 cubic inch small blocks to 6200 RPM on a 300-CFM Holley 2-barrel! Not the world's best choice, but that's all the track rules allowed.
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!