The 5831 is one of the smaller units, see the picture, I put the bottle of tea in there for size perspective. The big truck boneyards that carry these things will likely also have the shifters and the crossmembers needed to mount them. you would not want to try to mount them without them. the rear could be fabricated, but the front consists of a semi floating sleeve suspension to allow for a bit of movement under torque, without that floater, something gotta give
The boneyards that have them not surprizingly are in the pacific northwest and coal country ( log trucks dump trucks and coal trucks inthe mountains used lots of these things ) The new aux boxes available are twin countershaft boxes. They would work, but they would be extremely heavy and large and would eat up a lot of power in the extra drag, not very efficient for this size engine
The older boxes came in 3 and 4 speed models in various gear ratio combinations . anyone shopping for one of these things needs to do some research because you can't just grab one, you need to find one that is going to have a gear set that combined with your tranny and rear end, is going to be able to give you nice even splits between gears between direct and OD on a 3 speed and ud dd and od on a 4 speed, this becomes a little more complicated than it sounds because big truck trannys have evenly spaced gears while pickup trannys do not
the weight on the things range from 155 pounds for a 5831 up to 960 for a 9441 which is a pump lubricated model. The twin countershaft jobs get a whole lot bigger than that. I have a PDF file with a reference spec sheet with all of the specs of the things if anyone needs it, and I also have factory manuals for just about all of the old spicer trannys and aux boxes and PTOs
Bearings and seals are still available for the 5831, gaskets are not, have to use Locktite Gasket eliminator 518 anaerobic this is the recomended by the folks who now manufacture the spicer aux 1241 and the older unit replacement parts .Silliscum is a big no-no ( spicer no longer manufactures its 1241, it is now made by
TTC
they also have a bunch of manuals downloadable on their site on that page
Full rebuild kits are available for the rest of the aux boxes
here
A few yards that generallly have the things in stock
http://www.adelmans.com/atruckparts.html
http://www.a-atruckparts.com/Transmissions.aspx
http://www.andersonbrotherstruck.com/parts/?cat=transmissions
Driveshaft modification will be interesting. First thing I did when I picked it up at the freight terminal was drop by the driveshaft shop and he wsn't to concerned about it. IT's going to have larger joints on one end than the other but so long as it[s balanced , no worries . The smallest flange yoke that you can get that will bolt up to the pattern on these things is for a 1410 ujoint and the truck has 1350.
I'm still in the middle of cleaning mine up and getting ready to pop new seals in and replace the gaskets I don't want to dump a bunch of high dollar synthetic powershift transmision fluid on the ground. It had sat for a while, so I'm being patient with it floating some grime stains off the splines and such. I don't want anything coming loose later.