Good move keeping this one over the Coily, the coil SJs have a lot of weaker parts and the suspension on them really isn’t that great
If yours has the newer style gearbox then you can just buy a 413/samurai 5 speed and swap the front cases onto that to make a 5 speed 410 gearbox.
I have plenty of new style 4 speed boxes and would be happy to post you just the cases if you have an early gearbox and can find a 413/samurai gearbox locally (if you have an early gearbox you’ll also need a newer style fat gbox to tbox slipyoke/propshaft as well)
I have moved this to the builds area for you