First pic JM 35 sedan posted ,the one on the left is a 37 and later and you can clearly see the difference in the light switch bracket.I did a quick search and here is a link to a thread that will get you started.I have heard that its not necessary to replace the frame bracket but drill a couple new holes on the original 35-36 to fit the later box.I have done the conversion twice and it was well worth it.I did replace the bracket with a Bob Drake repo.Originals due turn up on EBAY.Finding a good 37 and later box might be another challenge as many out there are worn out.
https://www.fordbarn.com/forum/showt...ng+replacement