Underhood blower, should give bout 100 HP to the rear wheels. Try to find a 500 CI RB engine, I never heard of one until I was watching HP TV last night and, they had a '68 Dodge Dart ( I think ) and it had the 500 RB and, it was cranking 468 HP on pump gas then, they put a Blower on it for it to crank 711 HP.