I feel uniquely qualified to answer this one...

3875# '67 Charger running 4.10's and slicks

I ran my 446" at just under 500hp for quite some time, and the stock axles were twisting up. A set of Dutchmans solved that until I went to a 560HP 496" motor, then the Dutchmans twisted and I upgraded to 35 spline Dutchmans. This has worked OK, but now that I'm hitting it with nitrous, I'm just waiting for it to explode. The weak link is now the caps. The cost of the caps and machine work make it cost ineffective to proceed with this rear any more.

I bought a Dana 60 housing for $125, housing ends and perches for $100, a spool for $180, used gears for $75, bearing kit for $125, $350 for new axles and bearings, and $150 in labor to shorten the housing. Total: $1005.

Compare that to he necessary work on an 8 3/4. Mark Williams cap is $100 and $250 to machine and install it, and it will only buy you a little bit of durability. 35 spline axles are $350, spool to fit the bigger axles is $180. Total: $880

$125 is all you'll save and not have NEAR the durability. I got here incrementally, but I can sell off my parts to recoup some cost. Heck, I'll sell you my whole complete running 35 spline 4.10/spool rear out of my Charger and save you some effort, but you will not want to go any faster than 11.00. I've had it to 10.75, but I really don't trust it down there, thus the Dana.