Well with the 33s and added weight of bumpers and winch I really needed to improve the braking. I've seen where guys have installed a 95 double diaphragm booster. Problem is trying to find a used or even a new one.
So I looked into the difference between the TJ booster and the 95. The main difference is the length of the diaphragm rod. Here's a side by side of the original 91 and the 06 TJ boosters. There were two other things, the mounting bolts which are #10 metric bold requiring the mounting bracket will be drilled to accept them and lastly the brake lines come off the master cylinder on the opposite side...no big deal.
The 91 booster rod eyelet measure 7.5" off the back and the TJ measured 5.5". So to make this work I needed to lengthen the rod a couple inches. To start I cut the eyelet end off with about 1/4" of shaft length.
I then took a 1/2" coupler and drilled it out to 1/2" on the drill press. I cut a 1/2" length to be used as a coupler to weld the pieces together. Here's the finished product. With the threaded 1/2" grade 8 bolt welded to the eyelet I now have an adjustable length rod.
The coupler to mate the two together was drilled out to 1/2" to slide over the booster rod. Here it is the on the booster. The coupler will be attached with a 10-24 grade 8 allen bolt with a nylon lock washer. I'll match drill the coupler on the rod. There are predrilled holes on the coupler which will be used to tack weld it to the main rod. I didn't want to weld the front of the coupler to the rod for fear of potentially damaging the internals of the booster. I figured a couple tack welds through the holes wouldn't get the rod all that hot beyond the coupler. I also have a lock nut that will be used for the threaded section that isn't shown.