I have 2 cars with Wilwood kits front and rear, so here are my thoughts on the subject.
I wanted to have matching front and rear calipers for aesthetic reasons, si I took a Wilwood rear kit to match the front. So did a friend of mine, and I ended up buying his car (no, I didn't do the same mistake twice
)
If you want to convert the rear brakes, look into this first, and read around to find out if you want to retain the OEM tapered bearings or switch to Green Bearings... This has been covered on Moparts before.
In my experience, green bearings and road-racing don't mix. That rules out some of the kits on the market. Some people here might say the Green bearings are OK, but in the "Corners are best" section, I dare say they're not...
Depending on the diff you have, you may be able to fab a spacer to install between the axles, or you may not (with a Truetrac, you can).
Remove the center section and measure between the two axles for the spacer length.
Some diffs are not see-through, and you can't do this (or fab 2 spacers?)
You can also switch to longer axles
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It's much simpler to start by chosing a kit which works with tapered bearings. DrDiff has some (Cobra calipers with cable-operated E-brakes, I think)
If you install green bearings and take your car to a racetrack, the life expectancy of the bearings drops to around 20 minutes.
If you remove the inner seal from the green bearings, and don't drive too hard into corners, they'll live.
Oh, and the aluminum flanges on the Wilwood rear kit (which hold the inner drum parking brake) can bend. The parking brake is so weak it's barely noticeable.
If I had known all this before switching to discs, I would never have used a Wilwood setup on the rear.
For the front brakes, all I can say is that a 13" rotor, 6-piston caliper setup with 1.25" MC and hydroboost assist is great for both track and road use...