I have a 1988 GMC Sierra with a 5.7 liter 350 engine. it is not stock at all, 4" throttle body, performance fuel ignition, intake manifolds, cold air intake, and did i mention supercharged. it puts out about 585 horsepower. the truck is extremely light, emissions weight said 3255 pounds. I have gotten the truck to about 145 mph in 4th gear. it has 6th gear overdrive performance racing transmission. I was wondering what the top speed of the truck you think it would be.