Getting started

 México and Central America are much more dangerous now than back then.  It is unlikely, if you had anything better than an old beat up truck that someone would want it more than you and would make you an offer you would not want to refuse, at least if you put much value on your continued existence.

You will also find that driving your personal vehicle into some countries in S. America is not allowed. Some countries there have very strict import prohibitions for used vehicles.  And, driving with a US license plate in some countries would be about the same as putting a sign on the back of your truck saying "rob me, take my truck it's free!!"  

I assume you don't speak Spanish or Portuguese, necessary languages for driving in most of S. America.  And the driving customs are not quite the same as here until you get as far south as Chile and Argentina where there is a little more respect for the "normas de condccíon."  

If you are interested in traveling by car in S. America, I suggest you pick a country, go there and rent a car and you can have a really wonderful experience.  But try to learn the language and you will have a lot more fun.  Colombia has incredible sights to see, it is reasonably save (contrary to the old days when I lived there), and the people are truly wonderful.  But be careful or you will end up falling in love.  Chile, Argentina, Peru, are also good country visit destinations.  Stay far away from Venezuela. Guatemala, El Salvador, and Honduras are beautiful but best to be in good standing with the Mara Salvatrucha.  Brazil is also fun, but the traffic in the major cities is awful and crime can be an issue.

And most of all forget taking a vehicle and or camper, trailer, motorhome, etc. to S. America.  I would give my eye teeth to do it, but it just isn't possible.