Tailshaft swapping an RV 727, What output shaft is correct?

Yep, swap the tail housing and tail shaft and you are good to go. Be sure you use a 76 and up tailshaft, it can be from any 76 and up 727, sb or bb. There should be lots in light duty pickups still kicking around.

Your RV stubby will also likely have the desirable hardened input shaft. Look for a splash of yellow paint on the nose of the shaft.