I would stick with the car, but I am in a similar age group as you.
As far as gatling guns- not really needed- you take a boat around the Darien Gap, which is the worst stretch in terms of bandits.
Central America is more dangerous than most of south america- I am sure there are parts of rural Columbia you would want to steer clear of, but in general South America has very little active daily small arms fire.
I have a friend who is a raptor expert, (eagles, hawks, that sort of thing- not airplanes) he does a lot of work and research in Chile.
He has his american vehicle (a 4x4 Ford pickup) shipped direct from California to Chile, when he goes down for a season. This has worked well for him.