Hi JM, would your friend like to furnish some dimensions on the track frames and rollers, such as distance from the center of the pivot shaft to the center of the rear roller, the front roller, and the idler, and then the diameter of the rollers in case they're not the standard D2 diameter? I'm having zero luck finding track frames for my tractor so I'm going to build new ones. Since I'm using D3 rollers, which are a smaller diameter than D2, I might consider a five roller configuration if it fits the envelope.

Thanks Scott, unfortunately those frames are the pre-5U13273 short ones.
JM - I'm just scratching my head as to why it's so hard to find the longer frames given that approx 1/3 of all 5U D2s had them (about 6000 5Us and I don't know how many 4Us)
But more than one person has rebuilt his frames with new channel and plate so that's what I'm going to do. The only part that really needs to be salvaged from the old frames are the pivot shaft housings. I can also use 1" larger channel to avoid having to weld the strip along the bottom for the D3 rollers. What would be really cool would be to put the rollers in pairs on walking beams, getting suspension like a larger tractor. I suppose one could go hog-wild and make fully custom track frames with full suspension over the rollers and the idler : ) Probably easier to cut down D3 frames....