Need some help!

AndyF may have made an adapter for the Wilwoods to the factory 4-piston caliper spindles. Wilwood came out with 'street' 4-piston aluminum caliper a couple years ago. Main difference is sealing. If Andy has already made drawings, you might be able to get the dimensions from him since I don't think he's selling those adapters. Sear for AR engineering and/or AndyF over in moparts.com forum amongst other places.

The advantage of switching would be weight savings. Otherwise, really nothing. The 4-piston kelsey calipers are a very decent option. They are almost the same as used on Ford Mustangs and some Corvettes of the era. So pistons, seals, and pads are available. Good rotors are more scarce, and they are Chrysler only due to the small bolt pattern.

Pad type is D11. Many choices available.
Stainless steel pistons are available and worth it if the car sees moisture. The chrome on replacement pistons seems to be less consistant than factory.