A while back I was having intermittent starter engagement and thought it was my RD starter, so I replaced it with a new one. Turns out it was a grounding issue. (Engine ground strap was missing entirely, so for over a year my starter ground connection was made through... what... the shift linkage? Everything else is rubber isolated.)
Bottom line: I have an extra RD starter with maybe 30 starts on it, though slightly disassembled. Happy to let it go cheap.
Tom