50's cabs are wider than the early stuff, consider also using a d-150 frame.
Measure the width of the cab mounts and then measure the dakota and d-150 frames, pick the one that fits the best.
Shouldn't be a problem in that case, since cab is the same 1948-1953. Also the Pre-1947 Cab is the same too, minus a different front clip, dash and fender style. It's when you get into the really old stuff, or the 1954 and newer trucks that things changed.
Excluding maybe the 40's WM300 Military Power Wagon, pretty sure those used the same cab and bed as a 1940's B Series truck too