Can't you just buy what you want at a tractor salvage yard? The one near me has many 1010 crawlers with what you need. Macfaddens in Sharon Spring, NY. So does Smiley's a bit further down the road in Greene County, NY. I recently got tracks, idlers, and rollers from him for my 1960 1010 crawler-loader.
Note that the 1010 does not have the same tracks as a 350 if original. Tracks from a 420 or 440 will fit along with some other parts but the pads are usually two bolt instead of four.