Originally Posted by Full Tank
As mentioned above, if you can find a T18 out of a CJ you're golden.
The confusion arises when people try to use a T18 out of a ford truck. That's when you have to pay one of the adapter companies some serious coin for adapters.
The problem is most stock CJ T18's have the 4.0 to one first. This isn't nearly as desirable as the "A" model with the 6.3 granny low. They are also hard to find and fetch a premium price.
The 75 bellhousing may need adapting/replacing, as you probably have the T15 transmission.
My suggestion is a Ford T18, Novak or stock used mainshaft/adapter, 76 or later bellhousing from a 150/176 application. This will leave you with a fairly bolt in setup that may only require some driveline work and minor sheet metal adjusting.
The other option is a gear swap, however depending on your existing gears and what you opt for,, this may effect your on road drivability.