Your 9" issues likely were due to using too many factory ford parts. Everything but the housing needs to be bought aftermarket...and the housing needs a backbrace. Once you buy a GOOD centersection, you shouldn't have any problems. 9" are strong when built right, they just aint cheap.

CHIP
'70 hemicuda, 575" Hemi, 727, Dana 60
'69 road runner, 440-6, 18 spline 4 speed, Dana 60
'71 Demon, 340, low gear 904, 8.75
'73 Chrysler New Yorker, 440, 727, 8.75
'90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt
'06 GMC 2500HD LBZ Duramax