I am going from a 255 70 15 to a 295 60 15. I have 373 gears in the rearend. I was woundering what would be the gearing after I put the tires on. Also will this kill the performance of the truck towards the topend between 65 and 100. Trying to help the 1/4 mile time with this setup.

 

Well I'm not certain what your final drive would be but you're going to taller tires. You'll lose a little bit off the line but you'll gain it back as your gears will be slightly extended. Your top end should be a little bit better as well.