E350 Master Cylinder
I have been wondering for a while now what the best way to upgrade my brakes would be.  Over the years, a lot of things have changed in my braking system.  Larger front brakes and rear disc brakes are the largest changes.  For the past six months or so I haven't been able to keep the brakes bled properly.  I decided it was time to change out the master cylinder to something designed for 4-wheel disc brakes and perhaps offers a bit more leverage to compensate for the larger tires.  Also, my master cylinder is the original one that came with my Jeep when it was new in 1993.  I originally set out looking to install a master cylinder from a Grand Cherokee (ZJ), but learned quickly that the E350 was a better choice.

01/23/04 - Picked up the master cylinder
I drove to Napa today to order the master cylinder (part number 10-2008).  They said it would arrive at the store later in the afternoon.  It did arrive, but I didn't have time to install it before my trip tomorrow

01/26/04 - Started the swap
I started today by removing the stock master cylinder.  I compared the installation location and the threads where the brake lines connect.  The mounting holes on the new master cylinder are just a touch further apart then the stock YJ vacuum booster.  Running a 9/16" drill bit through the holes cleared enough material to mount properly.  As for the brake lines, they were each different.  The nut for the front brakes on the original master cylinder matched perfectly with the threads for the rear brakes on the new master cylinder.  The threads for the rear brakes on the new master cylinder are the typical 3/8" threads found on most of the fittings on the Jeep.  To make the new master cylinder fit, I cut and flared both front and rear lines after transferring the correct nut for each fitting.