You will need a trans from a V8 if you want/need overdrive. If you can deal without it, you can use a C5 trans from earlier RBV's and put a C4 bellhousing on it, allowing you to keep your ranger tcase. If you want to keep OD, then you will have to either get a kit from AA, or use another case. I'm about 80% done with my doubler build, and I'm thinking about building a setup that uses the ranger case. Only problem with that is it adds almost 10 inches in length, my doubler build is only 16 inches long including the reduction box and the tcase, with a ratio of almost 7:1, its well worth it!
You tcase options are the 1356 from the F-series (but frame mods are almost a requirement unless you make a trans X-member and move the trans over), the NP205 from earlier full size trucks ( strong and narrow, but a little heavy) and then there is the Dana 20 from the Early Bronco ( which is what I'm using), its small, relatively light weight (for being and all steel, all gear case) and the smallest in size. This thing is so small, it'll almost fit into a 15" rim
SVT