I`ve noticed my 12 bolt rear is crooked.Is there any alignment dimensions either from center of brake drum to back or front of wheel lip molding?I took measurments and came up about 2inch difference from driver to passenger side.Also what would cause that?All bolt holes line up.

 

Model/Year would help.

Here's a link to a 1970 (probably good through 1972). You might reach out to Tom (who posted) asking if he has other dimension diagrams if this is not applicable to your vehicle.
https://classicoldsmobile.com/forums...-frame-146230/

 

This may work better...

 

Measure wheel center to center on both sides and go from there.

 

The car had a incorrect 10 bolt when i bought it.Put the 12-bolt olds in and notice it wasn`t driving wright.Then notice the twist.

 

The fender openings are not the controlled dimensions. What matters is how the axle is aligned relative to the chassis.

 

Did the car drive OK with the 10 bolt rearend?

Was the O-Type installed with control arms attached, or were the existing control arms reused?

 

Chances are it's not the differential that's out of alignment. It's the frame to body alignment that is off.

 

I`ll have to measure the wheel crnters first,like 66 jetstar suggested.