Many of those may have been used by weekenders or drive2sit, so the mileage appears low for the age. The RV may be well used just not through miles.
I have a 94 GM 350-TBI paired to a 4L80 tranny. Mileage is over, well lets just say I'm thankful I only need to complete one odometer turnover affidavit and not one for each event! I do standard and enhanced PM on it and have only needed to change the oil cooler flex lines due to seepage and the oil pan due to a rock. Still goes strong with no leaks, squeaks or parts falling off.