The more rotational weight you take off the pulleys, the more power can go into the trans instead.
I think the largest single gain would be from jackshaft or crank pulley. I run AI jackshaft, water pump and supercharger pulleys. Not sure a butt dyno could tell it, tho, but w/other mods I'm enjoying 14 lbs. boost on my '90 SC that builds faster than when stock.