When I looked up the OEM chain for a 1983 XR350R, it said the part 14401-414-014 is discontinued. So, I googled that part number and got a page on ebay showing a replacement chain that says it also fits a 2006 - 2015 CRF450R. Not sure if the Honda OEM 2009 CRF450R cam chain would work on your 350, but if you want to try it, the part is on Revzilla:
Buy Honda 14401-MEN-A31 - CAM CHAIN. This OEM part is guaranteed by Honda's limited part warranty ✓ FREE Shipping on qualified orders - Partzilla.com
www.partzilla.com
The eBay page where I saw this:
For Honda CB250T 1977-1978. For Honda CRF450R 2009-2016. Chain Adjusters. Motorcycle Crankshaft Cam Timing Chain. For Honda XL350R 1984-1985. For Honda XR350R 1983-1985. For Honda CB250ND 1982-1983. For Honda CB250N 1978-1981.
www.ebay.com
I just don't trust aftermarket parts for an engine.