Phoenix Cruisers have swivel passenger seats and roughly a 2" height variation between the cab floor and house floor. There is lots of extra clearence if your motor home floor is a lot higher.
I would call the Phoenix Cruiser factory and ask who supplies their passenger swivel seat bases. The factory buys the seat bases from one supplier and actual seats from another. The mounting is generic with maybe 2 possible mounting stem centers. Measure your seat stem-to-stem, front to back and side to side, and have that data handy when calling that supplier. I am sure they will sell you a swivel seat base direct. If not, the Phoenix factory just might ship one to you.
Here is the Phoenix Cruiser website. Get the phone number here.
CLICK HEREHere is our front passenger seat swivelled. I wish I had a better picture handy. I do need to mention that neither front seat has an armrest on the door side. The seat might not swivel with an armrest there unless the door was open.