Brent,
If you're running reasonably skinny tires and rims that won't offset the position of the tire too much, you can get a good estimate of how tall you can go before hitting the underside of the wheel wells by measuring the distance between the top of the axle and the bottom of the rubber bump stops. Use that measurement to map out where the axle will be at full stuff, and then figure out the available radius. Leave some extra space for tire and axle dynamics (such as when one tire is stuffed and the one at the other end of the axle has daylight under it), and you should be okay.
It's a little more challenging to guesstimate what might happen up front, as clearances will vary depending on steering direction.
My favorite flavor of on-line speed calculator is Rick Grover's "Willys Utility Vehicle Speed Calculator" (you might already know about this):
http://www.public.asu.edu/~grover/willys/speed.html
Be sure to peruse Rick's "Discussion", just below the calculator.
If you're running reasonably skinny tires and rims that won't offset the position of the tire too much, you can get a good estimate of how tall you can go before hitting the underside of the wheel wells by measuring the distance between the top of the axle and the bottom of the rubber bump stops. Use that measurement to map out where the axle will be at full stuff, and then figure out the available radius. Leave some extra space for tire and axle dynamics (such as when one tire is stuffed and the one at the other end of the axle has daylight under it), and you should be okay.
It's a little more challenging to guesstimate what might happen up front, as clearances will vary depending on steering direction.
My favorite flavor of on-line speed calculator is Rick Grover's "Willys Utility Vehicle Speed Calculator" (you might already know about this):
http://www.public.asu.edu/~grover/willys/speed.html
Be sure to peruse Rick's "Discussion", just below the calculator.