Gen 1 Viper brakes reimagined

Good job. That gives me a few ideas for my project. Love the wood mockup. By using the spacer washers, you could make the brackets on a drill press. The position of the holes is not overly critical. Wouldn't take much to do it on a manual milling machine from thicker material and eliminate the loose shims either.
I was under the impression that Dr. Diff wouldn't sell the aluminum hubs by themselves, only with the kit?

I'd say the hole locations are critical if you want a nice tight bolt fit up. I don't see why you couldn't do on a drill press if you were precise with your measuring/centerpunching, etc. Fortunately, the spread on the spindle and the caliper are a nice round number. 3-1/8" on the spindle, and 100mm on the caliper. The measurement that took a few tries to get correct was the spread apart. I didn't have an accurate way to measure it, so it took some trial and error with the wood block. If you have a milling machine, you could certainly make it as you described. I don't have one. Honestly, .100" washer isn't a big deal. My understanding is most of the high end aftermarket brake kits require shimming to get the caliper centered on the rotor. Essentially, that's what that .100" shim is doing.
Dr. Diff does sell the hubs. I don't know how they compare in terms of location of wheel mounting surface. Meaning, does he make the surface 1/4" further back so the wheel is in the factory position once the rotor is on there?

FYI. Sendcutsend.com only charged $39 total to have these brackets cut. That's hardly worth the time to cut this out of 1/2" plate by hand.