Wilwood kit vs Dr Diff Wilwood kit, help??

Both kits are fine.

However, OP needs to measure the piston diameters for both Front & Rear calipers and calculate the Pedal Ratio. From there, call Wilwood and buy a Master Cylinder that has the correct Bore and Stroke length for the entire setup.

No sense in dropping a bunch of money on new brakes if the MC doesn't provide the volume and/or pressure you need to squeeze them correctly.

None of this "15/16ths" or "7/8ths" guesswork BS. Do the math. Call Wilwood. Be happy.
Good point, think i am limited on master cylinder due to running the 6.4 as fills the bay up quite a bit