Are you using the stock style single piston calipers ?
If so, I think the Wilwood Aluminum Master cylinders are specifically designed for their 4 piston calipers with 11" disks.
There are so many combinations listed that I think a call to them is in order to confirm exactly what's available for your combination.
(805) 388-1188
Also, their website shows a version of the Mopar master cylinder Kerndog was referring to but has a plastic body .
Wilwood Disc Brakes - Master Cylinders: Tandem Master Cylinder
If I was doing what you are , I would stick to a stock Mopar M/C.
