the "easiest" swap would be an L50 or L52. they are the 5 speeds found in '81-83 4x4s, and are the same length as your L43. the only mod you have to do is enlarge the hole in the floor. you'll need to grab the clutch set for the truck you pull it from, the slave cylinder, clutch hub and fork.

'79 sport 4x4 longbed <img src="/forums/images/graemlins/smile.gif" alt="" />
20/22R hybrid with EB's OS valves, 268c cam, offy intake, weber 32/36, thorley header, 5 speed swap, 34" LTBs, downey 3" springs, marlin hysteer, 4.88s and locked

'91 4x4 shortbed
22R-E, W56, the dd!