I had the same problem with my '48 4400. I pushed it around the farm with a tractor and loader pushing down on the back of the truck to no avail. Someone parked the truck 20+ years ago with the emergency brake on. The only way I could get the drums loose enough to remove was to get the truck running and run the truck on jack stands. Took a long time, working back and forth, and I had to chain one side to the frame when it became loose enough to free wheel. Then I cleaned and treated everything to prevent rust and corosion in the future. There's alot of work in your future,
Scott

Scott Ward

2 1948 1.5-ton Loadmasters
The red one and The snow pusher
1 1950 3100
1 1955.1 Chevy 6500
1 1954 Chevy 6500 2-Ton
1 1955 1st Series COE 5700
1 1963 K20 (454)
1 1964 C10 (350)
1 1951 1.5-ton Dump Truck
1953 and a 1956 Ford F800

Raising a teenager is like trying to nail Jello to a tree!