I also have a 52M38 with 11" brakes. I used google images and rock auto to figure out what they were off. Turns out they are off a 68 ford F100 or similar.
Good luck
Post a photo of the shoes.
Sounds like you picked up a fun project. I have a 73CJ that is about done. Always wanted a flat fender and looked around for over a year for the right M38. Did a 20 hour drive the week after Christma ...