I did mine using stock components. Look at the build thread on my '48 Chev extended cab. Using an extra set of complete hinge pillars, move the driver's side to the back of the passenger door frame and vise versa for the other side. Cut the outer door skins away from the inner. NOT THE SAME AS I DID IN THE PICTURE!!! Cut the inner portion above the upper hinge and then down below the inner door handle and window crank. I had to redo that section after posting that picture. By cutting it like this the upper 1/4 of it stays stock so your door handle location and window crank does not change. Then swap the inner halves of the doors from one side to the other and weld back onto the outer skin.
It sounds confusing, but not once you see it. I have pictures of this that I will try to post in the next few days.