if you are going to go 4age, its not as easy as it sounds (trust me I'm doing it at the moment), 1, you need custom mounts, 2, you need sprinter bellhousing/gearbox (the front bearing seals are different, however there is a way around this), 3, need to make new tailshaft and 4, have to get the bastard running :)
i would really recommend not working a 3tc/2tc they really are poo the G heads are somewhat better, but they are still old engines and hard to get bits for
and don't got 20v most over rated engine ever ;)
edit: i thought i should add re brakes, you should consider the rona/pug/hilux upgrade, corona strut,(rt132/xt130), peugot 604 disk (rda272) and hilux/landcruiser caliper (ln106/ln130) (4 pistons FTW!) as well as a late model camry master cylinder 2003-2006 i think (15/16th bore= you stop quick)