Is there a reason You feel the 8.25" rear isn't up to the task here??? Mopar used one to test all the B-engine packages in a 400ci Dart Sport for the bracket racer science pages. I personally beat the living bejeezus out of one in My ex Popo Diplomat, 383 4spd, trying to break it before putting a '68 RR 8.75 rear w/4.89's in it. I'm talking 6K side-steps, 2nd gear power-shifts, and as soon as the spinning topped out, I'd slam on the brakes & do it again..over & over. So long in fact, the guy riding shotgun starting saying "OK OK!!! We better get out of here!!!" Had another guy with a Dodge 4×4 w/a 400 in it to tow Me home,....never did...