Renwal - later Revell - made a collection of 1/48 scale cars that can still be found on Evil Bay. I have built a few of them and they are pretty nice, especially if you take a little extra time working on them.
Here are a few examples ...
1934 Duesenberg SJ
1939 Mercedes 540-K
1931 Cadillac Sport Phaeton in background
1940 Ford Sedan in foreground
They also make several from the earlier years like the 1916 Stutz Bearcat for example. Tamiya has gotten into the 1/48 vehicle game recently with some armor but rumor has it that they will be releasing a 1940 Ford sedan soon and just this month released a Citroen 11CV staff car that looks pretty good. Another thing to watch for are old 1/43 Matchbox vehicles - yes they are slightly out of scale but can still be useful in diorama settings. Lastly, there are a few pieces out by Corgi in the cast metal department that are 1/48. Their scale is not listed on the packaging so you have to look closely to find them.
Here is the Corgi Jeep in the foreground
Now, if you want to talk 1/48 armor there is a whole lot of old stuff from Bandai and some new stuff from Tamiya not to mention a wide variety of odd stuff from the resin producers. Here is a 1/48 scale Hanomag SS-100 from Matador ...
Hopefully that will give you enough to think about for the immediate future