well, horsepower at the crank would be before it goes through the transaxle and out through to the wheels. wheel horsepower is less than crank horsepower because all the power gets reduced when you put gears and other things such as wheels and axles in the way to move. your motor takes effort to spin these things. so horse power at the crank is just the horsepower before it goes through the tranny.

edit: there is no guarenteed amount of horsepower gains when you install anything on your motor. every engine reacts differently to mods even though it has the same engine code. manufactureers just give a rough estimate that is hardly ever right.