Measuring a drive shaft?

First when you DO measure be sure the weight of the car is on the diff.

Secondly, I would highly recommend calling the shop you intend to use and ask them how THEY want it measured, some shops have different methods. Best all around, that way there is no miscommunication.

When I had mine done, I didn't need to put the slip yoke in, they had me take two measurements, one from the flat surface on the rear yoke to the tailshaft end, and another from the flat surface to the end of the output shaft. It came out perfect.