If you are looking for accurate replicas, I would recommend again picking up Bandai's 1905 Mercedes-Benz. At best, it's a somewhat toylike representation of a generic 1900's automobile, but bears little, if any, resemblance to anything produced by either Mercedes, or Benz, in 1905 (they were separate companies until 1926, so there realy is no such thing as a 1905 Mercedes-Benz).
If you're willing to consider 1/24-1/25 scale, both Heller and Italeri make some very nice classic kits, with a fairly wide range of subjects. Jo-Han did make kits of a Mercedes 500K and a V-16 Cadillac, but they were in 1/25 scale, and I can't say enough good things about them. If you see them for sale, buy them. AMT did make a 1940 Plymouth, and their Chrysler 500C is very nice if you're willing to consider cars from the 50's.