"Today I learned"...
I THOUGHT I'd be able to swap out a Ram 2500 master cylinder. I can't. The bolt hole spacing on a WJ/ZJ dual diaphragm brake booster is about 3.5" and the Ram 2500 master is 3". If this wasn't enough, the center bore of the WJ brake booster is LARGER than the Ram master. Plus the WJ brake booster doesn't have a threaded rod I could extend.
So even the Dodge Dakota brake booster I just drilled apart trying to make fit won't work. The Dakota has about an extra 1/2 long rod to push the master. With the WJ booster I would either need to get some really strong small diameter rod to put in the booster to then push the master cylinder OR cram a bunch of random shit into the Dakota master cylinder and hope it doesn't fall out of place so the shorter rod of the WJ brake booster would give me brakes.
I'm sticking with the stock 2004 WJ brake booster and master cylinder. The internet says the WJ booster is a 1" bore. I'd still like a longer master cylinder so I could have more pressure for the disc brakes up front. This should be interesting when I go to stop the first or second time. The WJ is shorter than the Dakota, which is shorter than the Ram 2500. Waste of a few hours THIS was, and my goal was to get the Ram 2500 master installed so I could position the driver side shock tower instead of installing the tower, then screwing myself on the master. Oh and the Dakota won't fit in the WJ booster because the diameter increases in the last 1/2" so it won't sit into the booster fully. I really did consider putting a bunch of nuts and washers on the studs, silicone around the master, and giving it a whirl. I decided not to be so ghetto. Hopefully this thing can stop itself with two quick pumps.
Dakota on top
Ram 2500 on bottom.
Dakota mounting holes drilled out to 1/2” fit SNUG over the WJ studs. From the end of the rod to the inside it is about 2.125”. You can also see the larger diameter towards the end that doesn’t allow it to fit into the WJ booster.
Ram 2500. It measures less than 1” deep. Center to center is too small to fit on the WJ booster. It’s 1.75” diameter. The Dakota is 1.5”.
I think the Ram 2500 length would have been a SLIGHT problem with the shock tower location. It definitely would require new lines with new flares.