(not mine)
Actually a 400 head not a 350, but doesn't really matter since it needs machining. Maybe someone here needs a single replacement head.
This has been on CL for a long time. He was originally trying to sell it with a pair of cylinders and a RD350 head, and it was painted red at the time.
Yamaha RD350 cylinder head - $150 (Palm Springs Ca)
Yamaha RD350 cylinder head made by DG I only have this one $150.00
https://inlandempire.craigslist.org/mpo/d/palm-springs-yamaha-rd350-cylinder-head/7043610851.html