Why swap out the L43? I got one in my 79,and I was informed that they are not junk, the L52 5 speeds are the ones to stay away from...
not sure where you are getting your info buddy but somebody is confused
L43 has a 3.64:1 1st gear has a side shifter that always leaks and linkage thats doomed to be sloppy
the L45,L50 ,L52 and Marlins L52HD all can be bolted right into any 1st gen truck with no mods and all have a 3.93:1 1st gear and are topshifted, so no linkage at all