AX-15 and NV3550 are near direct replacement for the BA-10/5. Look at Advance Adapters website. I am replacing mine with the NV3550. Expect $850-1000 for a complete NV3550. Try to get a latter model AX-15 with the external slave cylinder. Don't know prices. You could swap in a NV4500, but you will probably have to body lift and/or cut into the tranny hull. AA use to sell T-5 for replacement, but thats 2WD. Also, with the NV3550, look at AA's slave cylinder adapter kit. Its what I bought. Its an adapted '75 Toyota Landcruisers slave cylinder.
Tom