What he said.
Some 38 Dodge cars had independent front suspension, some had the tube axle, seems one was an option? Which suspension does you car have?
I've had a 39 Plymouth body (nearly the same frame as your 38 Dodge) off the frame and it sat along side of an early 90s Dakota bare frame. From the rear of the Dakota's rear cab mounts, the truck frame is very different from the 39 Plymouth frame. The truck frame has a kick up and support members to hold the pickup box that would have to be modified to fit under the sedan. The Dakota frame also has kickouted front frame horns that would interfere with the sedan fenders, though those are easily removed. The Dakota frame is straight between the wheels where the car frame curves outward to about the center post between the doors, then back in to the front leaf spring mounts. The Dakota frame will likely either have to be shortened or lengthened as 117" wb or 133" wb was all that was available, neither wb likely matchs your 38. The Dakota frame and the 39 frame are the same width and height off the ground at the point of the sedans firewall and are a convenent location to splice the two frames. The X member is easily delt with during the clipping. You would have to fab up a radiator support, which is also the front fender support on the 30s cars.
The Dakota you seek would be the 1st generation, 87-90 because they have the 5 on 4 1/2" wheel bolt pattern. 2nd choice would be 91-95 because even with them being 6 bolt wheels, the older rotors and rear axles simply swap on/in. After 95 the old rotors and axles don't easily swap.
If you have independent suspension on your 38 Dodge, disc brake conversions and rack & pinoin steering setups are available as are front end rebuild parts. The independent suspension used on the late 30s Mopars were a well designed fairly modern system that, with a few tweeks, works well on todays roads.
Like said earlier, unless you plan on 500+ hp, the 38 frame will hold up well, provided its in good shape and not bent or rotted out.
As far as your equipment and abilities, we have no way of knowing. We usually begin at the point of questioning where your at, so we don't lead you astray. It was not in any means ment to short change you, simply to determine where your at. Gene
