806 and 856 shifting rebuild

Everything Dan said is correct. The plates with the ridges are what we call "detents" and can be changed by removing rivets. Basically in 06/56/66 shifting it does not have to be any one item. Rather, a small amount of play in the whole linkage can add up. Usually though, I have found the best area to start is the shift levers and ball& socket connectors. On one of my 856's I changed the bushing which the shift levers actually ride on. I.H. part man said no such thing until I took a picture of it. I don't remember the part # but it is a brass bushing found on the steering colunm itself. Also the High/Low/Reverse shift lever pivots on a bolt with a shoulder and was wore pretty good.Replacling both this bolt and the bushing took most of my play out without much cost or time. So in my opinion start with the shift lever pivot areas first. Most of the wear items can be found aftermarket to keep your costs down. I believe the yard I work at can even get an overhaul kit for the shifting, but I don't know what all is included or the price.

Iff the roll pins are loose, you could drill them out, but most of the time the play is tolerable. If the pins work loose, they can be held in by a small hose clamp.

You should find that the 56 shift requires less maintenance than the 06. One common problem on the 06 is that 1-4 has such a small range of motion to the lever compared to the 56. The same with H-R. Play just can't be tolerated on the older style shift as well.

Good Luck.