SBP Disc conversion keeping the Drum spindles?

When you're looking at the various different kits out there, there's a couple of really important things to check if you want to keep your current set of wheels. The first one is easy, make sure the wheel diameter requirement is going to work for you. Pretty much all of the kits will work with 15" wheels, but not all of them will work with 14" wheels. So if you're keeping 14" wheels make sure the kit you choose will work with those.

The second thing you need to pay attention to is a little less advertised, so you'll probably have to look it up in the specs for the kit. But you need to know the hub diameter on the rotor. The current wilwood kits are especially bad for this, they have a very large hub diameter and require the hub bore on the wheels to be 3.050". None of the factory wheels have a hub bore that large. So if you're trying to keep a set of factory drum wheels, or even a lot of the reproductions of factory wheels, you'll be limited again in which kit you use.

I wouldn't run the lower ball joints you need for the 9" drum spindles on the street, so I don't understand spending any amount of money if those spindles have to be retained. The 10" drum spindles already used a better lower ball joint, so if you've got a 10" drum spindle then the disk conversion kits to keep the 5x4" pattern make a lot more sense.