first off what kind of pistons do you have cast, forged if you have cast pistons I wouldn't recomend nitros. If you do run nitros retard your timing 4 degrees for every 100hp. your best bet for more power is a better cyl head the old double hump heads are great but the are collecter items now and exsensive to find and exspensive to rebuild for unleaded gas. I recommend finding some 882 castings these are unleaded heads cheap to find and cheap to rebuild and the flow about the same as 462. You will lose about half a point on compression but will make up for it on performance. 441, 487 or 041 heads are also a good choice but have same problem of not being unleaded. the cost to make them unleaded will be anywhere from $75 and up depending on machine shop. 041 heads are the same as 462 but they have accessory holes in heads.