The 450 is a great boat...but...I'm not sure the 45' length (and extra beam) of that boat would be better in all respects as far as the Great Loop. I've looked at some of the travel logs of others doing that trip and it seems that the marinas in some of the common stops were rather tight. A smaller boat may be beneficial when it comes to finding dockage. As far as as the engine choices, I would expect exactly ZERO people on this board to recommend gas engines for that boat, for that use case. Would make no sense IMO.