What he said... and I will ad my 2 cents because I have been through this. I bought a T18 D20 combo off of ebay a few years ago that was supposed to be a Jeep application. It had a funky bellhousing, input, and release bearing, but would bolt up to my 258. Bad part was that the release bearing was just about shot and for the life of me, I could not find a relacement. The harder I tried the more I found myself wondering exactly what the tranny and t-case had come out of.
I am an off the the shelf parts type of guy. When I swap something in, I don't want to have to search to the ends of the earth for the right part, gasket, or specialty bearing to keep it working. I want to go the the nearest parts store and tell them I need this part for this vehicle, even though it's gouing on my Jeep. I figured even if I found a source for the correct release bearing, eventually I would be searching to the ends of the earth again for the next item that wore out.
There is plenty of info out there on swapping in the Ford version of the T18, but the info I had found was hit and miss for the Scout versions.
I purchased a Ford input, retainer, and front bearing through the local parts store and tranny shop. Then I bought the adapter pilot bearing through Novak. Bolted the T18 to my T150 bellhousing, used the Jeep clutch, and put the whole thing under the Jeep. Simple and reliable. If any of the parts wear, I know just where to find replacements. The only thing that isn't readily available is the pilot bushing... I bought two so I have a spare on hand.
Unless your tranny and t-case came out of a CJ, which it obviously didn't, this is the route I would take.
Side note: During my research and when reading similar items about the Scout T18's I was told or read somewhere that the front bearing retainer on the Scout version has a different bolt pattern than the Jeep or Ford versions, making the swap I explained much more difficult to say the least. Might be worth verifying before you move forward.