Josh Boltrek is one of the really knowledgeable cruiserheads I have had the pleasure to meet. He authored the History of the Land Cruiser which is on the TLCA web site. A couple months ago someone asked about installing an H55F five speed Land Cruiser tranny into a later FJ40. Josh had already put one into his 1983 FJ40, and shared this:
If memory serves, the H55F is approx 90mm longer than the H41. You will have to change both shafts (longer front, shorter aft). The clutch is the same, but you will have to grind out the small dog-ears on the top curve of the hourglass shape on your bell housing from the H41. This is done to accomodate the small tabs on the H55Fs input shaft housing. Be certain to get the top loader from a 40 series (42, 45 or 47) so that it will allow the shifter to exit into the cab through the same hole as factory. You will also want to get the transfer case shifter linkage and lever from the H55F to allow your transfer shifter to function properly. On the H41 the mount is forward of the hump, and thus has a shorter centre pivot. In addition, the linkage is longer to allow the shifter to reach the transfer case. Also be certain that you get all of the bolts from the transfer case that came on the H55f, as this will allow you to more easily place your transer case on the back of the H55F. Your shifter from the H41 will work on your H55F if you cut 3/4 of a spiral off of the tensioner spring and get the little plastic boot that goes on the bottom of the shifter on the H55F. If you have any other questions, please feel free to contact me offline.
83 FJ40 'Piglet'
84 HJ47 'Patches'
"It is impossible to engage in true dialog with those that are closed-minded and intollerant... they are incapable of carrying on a dialog, only a monolog." ~Daisaku Ikeda