An update, I got to this today and have some information for you but not all the information.
Cascade/Super-Crawler linkage rod:
19 Inches long
Rod diameter 12mm
Thread length 22mm
Thread diameter 7.75mm
The rod is hollow almost certainly, I have used a lot of 1/2 solid steel rod in the metal shop, this stuff does not feel like that and it is magnetic. So it must be hollow.
The rest of the story, I did not pull the working gear selector rod because I only have "right hand" rod ends and did not want to break something and not have parts, I just ordered the left ones from MEREX. As you can see in the pic above I went ahead and replaced the right hand one since mine was really tired anyway.
Since snow season is basically over here for the season, I left the linkage out for now, not going to need the crawler gears anytime soon I think. Will put it back in when parts arrive next week probably.
If you still need me to yank the working gear linkage I can then.
Another option might be Schussler, they have a bunch of MOGs being parted out, when I was there last month I bet I could have grabbed what you need. They must have at least 40 Square Cab MOGs for parts. Super great people! In my opinion in the same league with MEREX...I like both places a LOT!!!!
On the other hand some steel pipe, metric bolts left and right hand (Belmetric) and a TIG welder and you would be set.