Are you talking about the transfer box? You'd need to fit the mechanical shifting mechanism. The vacuum shift in the transfer box was in the old 4 speed for the diff lock.
A V8 R380 gearbox would fit if you change the primary shaft and the mainshaft. The R380 has a shorter shaft than the LT77. the rear end of the mainshaft has a different oil seal carrier, hence you can't fit it directly.
Of course you can adapt the primary shaft of a 1994 generation R380, that would do the trick.
I'd rather buy a s/h R380 and recon it, that would be much easier.