Many parts are available either as "new-old" original stock or as modern reproductions. Let me know if originality is desired — I do have a stock of new-old original parts or excellent used parts.
Roller & Idler Kits are similar. Two seals, two clips, two bronze inner bushings, two steel outer bushings and a shaft. We supply complete kits at a slight discount, or the components parts separately. Parts for HG's, OC-3's, OC-4's, OC-6's are all the same, except the idler shaft & nuts are larger on the OC-4/OC-6.
Tip: these parts should always be lubricated with oil not grease! The oil is pumped into channels & galleries via a buttonhead fitting or "zerk". If your machine came with grease fittings, I'd suggest changing them out immediately. Many, many times I've seen excessive wear caused by the use of grease.
The one exception to that rule would be JD Cornhead Grease which works fine.
For early-style Cletrac & Oliver-Cletrac HG Idlers with the inside flanges (1939-50).
For later, heavier-style Oliver HG, OC-3 and OC-4 Idlers with the outside flange (1950 onwards).