Correct- 1939 are kind of 1 year only brakes on Fords/ Mercs. I believe Zephyr's got juice that year too... Bendix style.
yeah i know in 1939 the bolt pattern was 5 x 10.5 and '40 was 5 x 5.5 that's why i was wondering what year the juice started. will both 39' and 40' front brakes work on '37 spindles?