Can I drive an older car long distance?

I'm planning on buying an older car, either a 1984 Monte Carlo, 1999 Cadillac Eldorado, or a 2000 Ford Ranger and drive either one to Fort Polk from Miami since I'm PCSing there in a month. I was wondering is it a good idea to drive an older vehicle that far even if it is well maintained? Also how hard would it be to find parts and fix a classic car like the Monte Carlo?

Yes, you can.

Out of that list the most likely to be reliable and easiest to get fixed one would be the Ranger. Its a common vehicle that was not especially complex so finding parts or people to work in it should not be a big deal.

The Eldorado is a cool car but fairly complex and has a very complicated high tech high performance engine. You don't get that stuff for free both in initial cost, operating cost, and repair costs. Most Cadillac's were cared for by dealers when they were newer so the average repair places didn't get a lot of experience on them. Another thing about the Caddy is it prefers premium fuel so that too adds to the cost of operation.

The Monte is also a pretty cool car and may be the one I would choose but I have a lot of experience driving and repairing those sorts of cars. To the average person these days (mechanic or driver) that is pretty much an antique. Even the Ranger will have a better ride and handle better. Any newer car will be safer with crumple zones, airbags, abs brakes, and on and on. An 84 didn't even have fuel injection so they can be pretty temperamental and require more maintenance than an EFI car. Finding someone that knows how to fix a carburetor can be very difficult these days. They did have an engine computer but most shops don't even have the scan tool to hook up to these anymore and the info they could get was pretty limited so its a whole different animal when it comes to diagnostics. Basic mechanical stuff like brakes and tune up parts are no problem but interior and body parts have been out of production a long time and very little is reproduced so stuff is hard to find and tends to be expensive when you do find em.