Cessna 310, you can get some of those cheap too, and if you want to, fly it fast, if you want more time, fly it slow, still going to be relatively "cheaper" that way. Pulling 21-squared, you'll probably be burning less than 20gph easily on a C310 R-model, especially an older C310's with the IO-470's should net around 18gph. You can always go slower!