Viper brakes 73 dart

You need 73-76 A body DRUM spindles to use the AR Engineering parts and pieces, to do the Viper caliper conversion.
Their parts are designed around the DRUM spindles, so your existing disc spindles don't work with their parts.
And NO, you can't use 72 spindles either.
Different inner wheel bearing diameters.
I have sold quite a few Drum spindles to do their conversion, but currently i am out of stock of them.