Jon,
I'm interested in your RD400 if you have it still. Check your PM and email.
Here are pics of the 2 RDS I'm trying to track down. Plus an RZ350 frame that had an RD250 motor modded to fit it.
Here's the bike that now has a yellow frame, otherwise everything is the same.



This red/white bike is an R5 frame that last had an RD400 engine. Registered in Idaho to Schultz. Sold to someone on eastcoast long ago, early or mid 90s?