Changing Drums to Disc

Wilwood is ~$750, Scarebird ~$350 and even cheaper if you buy just their brackets (~$105) and source the GM/Toyota parts locally. You will have to drill the Previa rotors for the 5x4" pattern (now and in future), but they provide a template, or buy pre-drilled ones from them. Wilwood parts might be expensive or "not avail" in the future, though they have been around a long time.

The only disadvantage I see in staying with 9" spindles is that the wheel bearings are a bit small (A1 & A3) vs the larger ones (A2 & A5?) w/ 10" drum spindle. Both outer bearings failed (spun races) in my 69 Dart w/ 9" drums. This is only for Scarebird, since I suspect Wilwood's hub uses larger bearings.

Going to "correct" K-H disks and spindles would be ideal, but the price is very high (post 11) and parts may get scarcer, save ones that interchange w/ Mustangs. They also may not match your fender tag anyway, if the disk option shows on that.