Thanks for the links Grigg. I have a NAPCO 4x4 setup on my 55 3100 shortbed. The truck starts screaming at 45mph so it would be nice to have that extra gear for tooling down the roads with 55mph speed limits. The problem is that it has a divorced transfer case so there is limited space between the tranny and the T.C. I was hoping that an overdrive would fit on the side of the SM420 where the PTO cover is rather than the back of the tranny or transfer case. Though I may look into the gearvendors because they claim that you install on the back of the T.C. with no need to modify the driveshaft. My only other solution is to get an NV4500 but it is 7" longer than the SM420. I have room to move the engine forward, but it would be nice to keep everything where it is. I could have a custom built mini shaft made. What is the shortest shaft that can be made? I think after the NV4500 went in I would have about 6" left for a shaft. And it would need to have a slip shaft for movement.
