According to the book I have, a 40 Dodge through 48 Dodge lists a 119 1/2" or a 139 1/2" wheel base. By 49, wheel base depended on the body series.

Chrysler lists a 122", 139 1/2", and a 128 1/2" and 145 1/2" wheel bases for 1940.

Desoto lists a 122 and a 139 1/2" wheel base for 1940.

Plymouth lists a 116", (2) 117" and then a few long ones (over 137") for 1940.

So according to the WB you will need a frame from a Dodge only between 1940 and 1948. The 39 Plymouth and the 47 Plymouth we had used the same front and rear suspension. With that in mind, I suspect you would be safe looking for a 119 1/2" wheel base frame from a 40-48 Dodge. Gene