Most people will tell you to use the Ford 9"--- except me.
Chrysler 8 3/4 is a good choice for what YOU plan to do, They offer more room for your legs, good gear sets are available, less exspensive than a Ford build, Not that it really matters but a Ford eats up a touch more HP because the pinion is lower. Don't go with a diff, spools are plenty cheap these days for them and available in the popular spline counts. With todays tracks and tires they will handle 800HP easily
Chrome Moly is so much eaiser to work with them DOM mild steel and the cost difference is a couple bucks, Places like Aircraft Spruce sells Moly at a reasonable price and will/can sell only the amount needed without cutting charges (as in ordering 2 -6' pieces instead of a 12"). Proper planning and the material can be shipped in short runs instead of freight shipping a 20' length.
Front torsion will add another $400+ to the build and not really needed because current rear tires do most of the work and a solid front end is fine, A piece of 1 3/4" X 120wall and the split front axle will slide in or you can split the 1 3/4 and clamp the full axle in place