I was wondering if we could have some sort of reference guide for donor bikes?

Stuff like:

Bikes that definitely have frames that seem made to be converted
Bikes that you may think are ideal, but once you crack them open, there's no room for anything or at least anything worth while.
Bikes that maybe good if it wasn't for the lack of parts etc

I was looking at a Honda Spada and my mate shook his head and said no, because lack of parts etc. That bike was made for Japan and Australia/NZ, and I'm guessing there wasn't any really aftermarket range and gen spares.