D2 Tracks

Here's another current problem I have. My good D2 5u has worn out tracks. It has 30 links and actually measures about 70% worn. I got another D2 5u that has good tracks but is other wise not in real repairable condition. The tracks on it measure about 20% worn. I would like to switch 'em.
I've been told that the good tracks are 'late model', 'good ones'. They look good! But, and here we go with the buts again, The worn tracks have 30 links like the parts book says but the newer, good tracks have 31 links! Honest to God, they do! I even had somebody else count them. The sprockets look the same and have the same number of teeth.
Where do I go to get answers to this curiosity?
How do I find out if the good(better) tracks are in fact,"better', and what make they are?
And then, how do I start to go about changing them. If I knew what kind of tracks the new ones were, I could maybe get a book or shop manual for them...
The guy that told me that the new tracks are good was at the auction and I'm not sure I can find him again...., Oh yeah, He told me the maser links on the 'good' tracks were new style, easier ones.

Late model D2 are longer than the earlier ones and have more pads. They lengthened the machine so that the main clutch may be removed without removing the engine. Just make sure that the pitch of the links is the same as your old links.

Buy them before the scrappers do!
I run 31 links on an early J model with the larger front idlers for carrying a blade.
Good rails are very scarce!

I believe all D2 and R2 used the same track chains, If memory serves me the larger front idlers also required 1 extra link.

So if you have large front idlers on 1 and not the other switch the idler and the chains, if not take out a link.

My late model D2 calls for 32 pads in the parts book--but the machine actually has 33 pads per track.