Spring Perches question

Doesn't it GREATLY depend on the angle of the drive line (crankshaft/trans)???

Treblig

Oh heck yes it does, but generally we assume the trans is where it always was.

It's a three point measure.
Vertical measurement of the end of the trans, then driveline angle itself, then rear end vertical measurement. (plus your estimated torque movement)

Basically you want the same but opposing angles at each end of the driveline. (plus the torque twist estimate added at the rear end)