I know this an old post, but I have made some changes to my plan on my truck and am curious as to if the changes will affect my times at the track. The engine mods I listed above are still the same. However, the reared and tires have changed based upon what I have sourced within the past few months. I should have the motor running this weekend but the suspension is going to have to be put on the back burner until I move homes. Anyways, I now have a set of 25" skinnies for the the front and 31x10.50 slicks for the rear and the rear is now going to be a Ford 9" and ladder bars with a detroit locker and 4.56 gears. What kind of times should I expect? Any different?

 

That is a very tall tire IMO unless you have gobs of power. I have 410 gear and run 28" max, but sometime run a 26"

I can't guess with a 31"

 

4.88's with a 31" slick for 1/8mi

 

Yep...4.10's with a 26" and 4.56 with a 28" if you are talking 1/8th mile stuff..