I am a short-legged 5'5", wife was 5'1" and we found the seats fitted by Winnebago to be small enough to fit us well.
Your seats were most likely 3rd party, fitted by Gulfstream, because Gulfstream did not manufacture seats and the RV upfitter's package for the E-series cutaway included no seats. I would have suggested looking into the Ford seats (there were at least three versions, XL through Chateau trim lines with the Chateau captain's chairs being most adjustable) but you've ruled out those options by sitting in a friend's Ford.