Gdads
I originaly had the disk breaks on a 1949 fleetline project. Based on what I have seen in the manuals the 49 (fleetline) and 56 (3100) spindals have the same dimensions. what I dont know is if the backing plates have the same bolt patterns.
Another posibility I have contemplated is to find 6 lug rotars.
The Goal is to keep it as simple a posible and minimize the snowball effect.
If all else fails.
I dont realy think keeping the drum brakes would be an issue for driving in the Kansas City area.