brake problems?

[sluginxlt]

my 1967 has all drums, i was driving it daily while i was doing a solid axle swap in my ranger. some times brakes would feel soft the first few minutes and other times the first few minutes of driving it no matter how lightly i tried to push the breaks they would lock up but after a minute or so they would go back to normal. So i finished the ranger and the fuel pump went out on the 351 gmc so i let it sit all winter do to lazyness. I found a fuel pump and got her running, but when i went to stop, no breaks! All the fluid was gone out of the master cylinder but never seen any leak on the ground or anywhere on the truck. any ideas on what happened? also when i was driving it daily break fluid would slowly dissapear but never seen a leak.