Originally Posted by Kreep
The reason for the lip sticking past the cover is that the cover is the same on D60 and D70 but the D70 housing is beefier.
On a D70, the axle tubes neck down before entering the brake drum. This makes narrowing a pain, but does help with identification.
I just purchased a Dana 70U (marked 70-1SU) supposedly out of an '86 E350. It's tubes do not neck down like you state, which should allow me to narrow it easily. Just thought I'd throw this out there. I guess there is some variation in the housings.