Crabbing

RustyRatRod said
The first thing to do is make sure the car's frame rails are square according to an X measurement. If that's good, then I would measure from each leaf spring center pin to the front leaf spring mount. You'll find it somewhere.

Or , u could just tape measure from the trans. crossmember to the rear axle shaft, compare both sides , no need to make it harder than nessesary .