Horsepower losses through the drivetrain depend on components used. My friend Jimmy's S-10 has been both engine and chassis dynoe'd. It was a 522 on gas so I won't bore you with the numbers. He did both to (a) see how much you really lose and (b) get a baseline so he didn't have to pull any more engines to dyno tune further. He had a glide and a 9" with "small" slicks (10X26's). His losses were right around 28%, which is pretty standard according to the dyno guy for any automatic/9" equipped car. Stick shifts with a 12 bolt/8.8 style rear are generally around 20%. These are just swags. The smaller the tire, rearend gear, and trans gears, the less you lose, but the less your setup can handle.
