Since this is a pro touring website I'll chime in with my results from a pro touring car.
I had the engine dynoed and then a chassis dyno. It worked out to 16% hp loss and 15% torque loss. Big block chevy, tko 600, 3.5" aluminum driveshaft, and 12 bolt with 33 spline axles.
There is only one way to figure it out. Do as I just said...