After talking with both Baer and Wilwood plus dr diff, a stock drum/drum prop valve can be used no problem so no need use an adjustable on at least with the 11.75F/11R
I find it a little hard to believe that the rear calipers in those 3 kits need the same amount of fluid/pressure as a set of stock rear drums, but if they say so.
Regardless, if that is true, it means that those disks provide the same amount of stopping power as the stock drums.
Heck, I think I'd feel better about the adjustable prop valve and "dumbing down" the rear disks. At least that way you're not already maxed out on your rear stopping power if you upgrade the fronts again.