Pretty sure the car housings had 3" tubes and truck housings have 3.125" tubes...or is it 3.25"? I'd have to crawl under one of mine to measure. Tube diameter isn't a big deal...got my U bolts from NAPA.

There are 2 different housings...the standard Dana 60 and the Dana 60 HD. The HD is heavier and has an extra strengthening rib across the top of the housing.
The HD is fine to use, just a little heavier. Some prefer it b/c it also has thicker tubes too IIRC.


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