for the average rwd car a 10 percent or less loss of power between the crankshaft and wheels is excellent.....
IE u have a 500bhp@crank mtr x .10=450whp@ the wheels....
, problem with that is that a stock t350 GM trans in good condition w/stock or loc up converter takes 23hp to operate, a typical driveshaft in a camro/firebird another 3-5hp, an 8.5 posi rear, which is what Z28/Trans Ams come with is an 11-15hp loss depending on gearin, then u have loss for the weight of the axles and driven wheels to account for, thus, tho .10 percent is great, a 15-20 percent loss is the realistic average...