Curiously that's where I bought the Ram from, Miami Beach in fact ! I think you're right with the gearbox being shared with the diesel. I'm still having no luck over here getting a replacement casing, or even a complete gearbox for that matter. Have you been over there long enough to have any contacts that could help ?
Yeh, the petrol is pricey but I've always got 15/16 mpg (British gallons) on a run which is all it ever gets used for. It was a mid-life crisis 10 years ago and I find it really frustrating with it off the road as I'm a furniture maker and used it for everything to do with the business.
I had a great contact in Sarasota but unfortunately he's moved on so I'm at a loss to know who might help now.