https://www.ebay.com/itm/Yamaha-tz350-rd350-vintage-DRAG-RACER-Champion-frame-r5-rd-350-racing-250-AHRMA/203045780129?
That has some interesting parts. I imagine someone is out there salivating over that front brake right now.
It looks just like an R5 hub with holes in it !! I have 2 right herewith holes