Dad and I did this with the TD8 once. Got him through the summer. Take the master link out, take the pad off the link next to it (either side), and then beat the next pin out. Seems to me we ran it back under the machine to keep it from moving and welded a freestall neck rail bracket onto a piece of old tractor drawbar to hold the piece of truck axle we were using for a punch in place. Then pull the sides together and use the master pin and bushings to put it back together. Save the spare link, if the rail measures within spec when he does the undercarriage he may be able to have it pinned and bushed and will need the links to put back in.
On salt tracks you'd need to knock out two pins and put one back in.
Let's face it, anything that the shortened tracks will wear is already shot as well and needs replaced. When we did this the sprockets were also already gone so we threw a set of them on. When we did the undercarriage we set them aside as spares, as they were worn but still serviceable.