I have a Suzuki Samurai and a Jeep. The Jeep is 180hp 4k lbs and the Sanurai is 60hp 2300lbs. The Jeep runs a 33x15.50 and the Samurai runs a 31x11.50. Both are the same brand of tire, Super Swamper TSL. Now this aint drag racing but the Samurai will definately climb a muddy hill (level, no ruts just slick greasy) the Jeep will spin the tires more and will definately accelerate better. But the little light weight Samurai will climb better, hold a line better and not slide in off camber situtions. Weight plays a huge factor in how a car performs. I think in a weight distributing, traction perfect world, a 2300lb 7.9hp per lb car won't accelerate like a 400lb 7.9hp per lb. I have no scientific or mathmatical evidence but I would assume that the hp per lb would have to increase slightly. Maybe a small percent, like 7.9 to 8.1.