Don't forget a bank account for gas!
My 86 318 "Ram Van Royal" 150 (109" wheel base) would muster 13 mpg around town, and almost 16 mpg when you stretched it's legs. I can imagine what an inefficient boat that would be with a 440, stretched frame, dual axle, probably geared very low, and the added weight of that large body and it's interior appointments.
Can you say 10/13 mpg? lol