How to add a disc brake to front wheels to replace caliper brakes

Custommotorbicycles has a spin on disk brake set up that requires a freewheel in the front but I don't think you need a fork with a disk brake tab.

Im going to disk on my next build, triple tree fork with the disk tab and k-balling the front hub and disk set up from another one of my peddle bikes that I don't use much anymore, or something like that lol. Plans always change....

Dan.

So, theoretically, if you keep braking in reverse, you will be able to unscrew the disc off of the wheel?