Power train loss???

I was curious how much power loss there is in a drivetrain. I know in a manual it is about 18%. How much power loss is there on a TH350 backed with a 8.5" 10 bolt with posi and 3.73:1 gears. I know it would just be an estimate. Is it around 25-30%? Thanks for any info. I have a friend who just took his 69 Camaro to the dyno and it put down 370hp and 429ft-lbs of torque at the rear wheels. He has a 3500+rpm stall converter, a 400SBC, a TH350, backed with a 12 bolt with 3.42:1 rear gears and posi. This is a nitrous motor on a dry run. What kind of power loss should he be seeing?

i beleive that your right on the money core402

with autos ive seen people use numbers from 20-30% power loss, depending on the application...