how hard is it to install an sj 410 t case into a 1987 samurai?
Depends on what year of SJ410... For example if you have an '85 SJ410 from the Canadian market it will bolt right in with no modifications to the early model (small flange) US Samurai, drum brake and all. However, as you get further apart in years there are increased chances of it not working without some mods.
Good Luck, Eric