btcamaro

a friend of mine has a tpi 383 with vortec heads in his 81 chevy truck, the truck has a 700r4 transmission and 3.55 gears and 28" tall tires. We have been fighting this detonation problem for a while even before the 383 and we cant seem to get it to go away. We have all of the diy prom stuff and have played with the timing with no luck. I was thinking that maybe with this big of a truck that it needs more gear to help pull it. what do you guys think.