Hey Bobby,
I have a 29 tudor that is low low low!
Your frame dimenions will be determined by several things.
Your engine that you are useing,tire /wheel height combo,axle set up(suicide or other)spring rate, ect.
I suggest you set the car body up at the height you want it and "build" you a mock up frame from wood 2x4's to find the length/height of the real frame measurements with all main components and record those measurements.Remember that everything will be quite a bit lower once all the weight of everything is in so ajust with where the springs mount.Setting the body higher than you want is better than too low and work from there!
Hope this helps?
Tim