Bellhousing alignment...

That appears to be the correct way to set-up one of the measurements. But, you must also measure insure that the face of the bell housing is parallel with the face of flywheel, so the transmission is both square with the crank centerline and the transmission shaft centerline is in alignment with the crankshaft centerline. I don't see the picture of the set-up to check the squareness of the transmission mounting face.

How would I set that up? I've read some people put the magnetic base on the oil pan, turn the motor over and check the surface of the flywheel... is that correct?