On the KIWI site in the tech section you have a very good assembly instruction. Relevant specifications can be used for the Scout box.
http://www.kiwiindian.com/#!transmission-3-speed-installation/c2jt
There is 3-4 things that I don't agree with in the instruction. One thing is the lockwasher he is using for the clutch basket nut inside the gearbox. He is using a finger lockwasher and I think the fingers are way to narrow to be effective.
I like to use a full circle lock washer where I can fold a larger portion over the nut. And I am meticulous to fold it close to the hexagon corner at the end where it has the largest momentum for preventing the nut from loosen up. At the other end I can leave a little gap where I more easily can get a grip with a screwdriver and pry the fold open at disassembly.
In addition I drop a small drop of penetrating green locktite on both sides of the lockwasher immediately before I tighten up the nut. Some of it ends up on the threads.. Penetrating green is soft setting.
Another thing I don't agree with is that he whacks the nut with a blunt cold chisel. I use proper tools specially made and can if I want, torque so hard that I strip the threads! I can not see the benefit of whacking the nut and risk damage the hexagons so I get problems later with fitting the tool or chip the nut. I tap the nut a little anyhow when I fold the lockwasher.
Well, there's still another thing we don't agree on...I am not that meticulous when it comes to the side play for the cluster gear, I think it is absolute minimum with a sideplay of .010. and can accept up to the double.
I would strongly recommend to use a 2RS bearing, double sealed rubber sealed bearing because the bearing doesn't need additional lubrication other than what's in there from the factory and the oil in the gearbox is fouled with gear shavings and clutch debris that will wear the bearing in short order.
On the Yahoo site for the 101 club, you can find in the photo section a couple of albums about the gearbox assembly (Transmission and Transmission 2). Read the comments, you have to click on a tiny symbol on the picture.