I have two spare rear ends, one is a 9 bolt with a gov-lock posi and disk brakes, the other is a 10 bolt with unknown posi unit, i believe currently 26-spline axles and aluminum drum brakes.

I am building a 400ish HP 383 with a TKO 5-speed behind it, the question is which rear end am i better off building up to handle the power?

 

The 9-bolt is somewhat stronger. IIRC, the 9-bolt wasn't equipped with a Gov-Loc, so you might considering verifying as the Gov-Loc has a very poor reputation here on TGO. Disc brakes are a plus and the 9-bolt would have 28-splind axles. Parts are more difficult to come by.

Here are a couple of links that might influence your decision:

https://www.thirdgen.org/forums/faq-...now-about.html

https://www.thirdgen.org/forums/tran...-10-bolts.html

JamesC