Donald’s car and Scrooge’s limo are both cars from roughly the 60s.
The limo I’m fairly certain is referenced from a 1964 chrysler crown imperial ghia, or a 1960/64 Mercedes-Benz limousine.
Don’s car, meanwhile, is a woody wagon; probably a 1963 Ford Fairlane station wagon, though much more compact. And, obviously, having GPS nav that a woody wagon would have most certainly not had in the 60s.
Other cars in the show DO seem to have the very boxy look of the 1960s and 1970s, though with how generic they are it’s a bit hard to tell.
Do Scrooge and Don just like retro-fitting old cars? Or is it as I suspected: possibly an alternate universe where things progressed much faster than they did in our world–as is canon to the old comics.