Those old rear ends are as tough as woodpecker lips! Lots of us dirt track racers in the 1970's ran them behind 500+ HP small block Chevy engines, turning over 7K RPM down the straightaways through a Muncie 4 speed locked in 2nd. gear. That's one reason the 4.10 gears are so hard to find- - - -that ratio was perfect for a "long quarter mile"- - - -a track that measured 1/4 mile around the infield. A "short quarter" measured around the outside wall, needed a 4.56 gear to get the right engine RPM.

We ran at Merced, Watsonville, and Antioch California, in the San Joaquin Valley back then. Merced was a "short" track. The others were longer, and we had to swap rear end centers to run them.
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!