You probably never looked up how to calculate horsepower. You can put your car on a chassis dyno and that gives you rear wheel horsepower only ( at least that's what they only show when they test your car's power, I've never heard of them giving flywheel horsepower on a chassis dyno.
You can only guess what the flywheel hp numbers are from chassis numbers. It's gonna vary with the various drivetrains some are gonna eat more hp than others.
