From the English magazine "Farmers Weekly"

Massey Ferguson is the latest maker to announce that it will offer tracks on its combines.

This is significant as it now means that all the big combine manufacturers – Claas, New Holland, MF, John Deere, Case IH and Deutz-Fahr – will soon be able to offer in-house tracks as well as tyres on their machines. And some of the makers believe that a high proportion of their bigger models will go out with tracks rather than tyres.

Details of the MF tracks are still sketchy, but the plan is to use the well-tried track technology from Agco stablemate Challenger as the basis for tracks on its larger eight-walker Centora and hybrid Delta combines next year.

Two belt widths are likely to be offered and the fully integrated system will initially allow speeds of 30kph, with 40kph machines possible further down the line.

We haven't seen any pictures of what the tracks will look like but our artist has used his imagination to magic some unfeasibly big Challenger tracks on to an MF combine to whet your appetite.

I have not seen the pictures, but, am i wrong when I remember that the regular metal tracks have been offered on most self propelled.  I believe they were made to work in the rice area.
I have nothing to support this but I seem to remember it being available as an option.
Good Luck!
Bill Long
ps:  If pictures are drawings are available I would love to see them

The Greene ones had a track option back in the 70's and 80's.Don't know about Gleaner.