Before anyone orders a Corbin seat for a R65, you better check with Corbin. A couple of years ago, I wanted to get a Corbin for my R65 (1982 dual shock). I saw a listing for a mono shock R65, but not the earlier ones. I called them, and learned that they no longer made them for the dual shock models. Things may have changed, but check before you place an order.
FWIW, I put a Corbin on my K1300S and love it. It is great for all day riding, and long distance touring.
k_enn