diff ratio, much of a difference?

Not sure of tire diameter so I guessed 27 inches.

That means if you are in high gear you are crossing at about 4K.

A 4.10 puts you at about 5500. You need to know how many RPM you want to trap at, exact tire height and do the math. If it's a drag only thing, you'll need at least a 4.56 for that, if not a bit more.


How much converter?