I had a 39 Plymouth business coupe that had a 1st gen Dakota rear axle under it. it was a very good fit with 15 x 7 wheels. Those were about as wide as a guy would want to go, and that wheel was centered in the fender.

We clipped a 39 sedan with a Dakota clip, it fit real nice frame, matched up perfectly at the firewall. We split the 39 frames "X" member and slid the Dakota inside the 39's frame, but we sold the car before it was road worthy. A 39 has the same frame as up to 49. Have no knowlege about car frames newer then the 48/49 change.