I just turned an FS into an FSO its pretty sraight forward, get an input shaft, countershaft drive gear, and O/D gears for main shaft and counter shaft. You will need a press for the countershaft gears. The best prices for parts I found Was Global Drive Train supply.
iT IS GOING TO BE A MATTER OF COST You have to have a very reasonably priced FS6406A 1st , and not just some core, because you are still using a lot of what is in that transmission, then you need the gears and then, in my case, a mechanic to put this together. For me the cost will come out about the same.
It would be nice to see the parts sheet and cost so a call can be made on how to go. Somebody could make money putting out a conversion FS- to FSO kit... and also just finding the transmissions and selling the completed FSO. It has to be an FS6406A to start with.
Fuller changed some of the technology from the FS6306A. They were re-engineered with heavier synchronizers and other stuff which among other benefits was a significant less shifting effort. Guys might not mind shifting a heavier transmission, but the wife or girlfriend, even though they may prefer shifting gears may balk after fighting the synchros or grinding gears when they fail, in an older series FS Fuller 6 transmission especially if they are driving the truck and pulling a loaded horse trailer or 5th wheel and end up doing a lot of downshifting for hills and traffic. The FSO or FS6406A are the newest version and have been out about 10yrs, if that. Earlier FS6's did have some issues with synchro failure and could be tougher on the arm if you had to do a lot of down shifting.
My truck is a daily driver and I want it as easy as possible for the lady to drive. I am using the entire Ford hydraulic system out of an F650 that was bolted on to a Fuller. I had a really bad experience years ago, where the pedal effort was so hard that I had a block of wood on the pedal to give me enough leverage to floor the clutch. I am being told now that the linkage was just a little bit out of line, but it only takes a very small fraction of an inch to screw it all up. It may look perfect... But..... The other bonus is the hydraulics do the adjusting, no getting soaked sliding underneath adjusting the pedal linkage.
Looking forward to see the cost breakdown on the conversion parts. Reasonably price FSO's are rare and there are lots of FS6406A's out there.