Aaron Coolidge wrote:

[snip]

Has anyone had success just replacing the drive unit?

Yeah, I did it recently on my PA-24-250. I'd originally planned to
replace the starter with a new lightweight model, but after discovering
that the only one that would fit without having to move the oil cooler
was back ordered I simply replaced the Bendix. It's trivial to do; mine
had a single roll pin holding it in place.