Breaking Question

[Tachout]

Today I drove my C20 to work for the first time. It is the factory Drum Brakes. It has been a while since I drove a vehicle with drum brakes. They leave a lot to be desired. Everything worked fine till I hit the offramp. The brake pedal got soft on me. I was on them pretty hard, but the pedal was soft and fading to the floor. I down shifted, and slowed down, and when I got around the off ramp corner, and down the hill I slowed down. Got pulled to a curb and as I stepped on the brakes they were normal again. Finished the 4 blocks and 2 turns to work and again the pedal was normal. Got out of the truck, came in to work, and got all set up. Went back down and checked the fluid. Fill and clear. I then checked the pedal and it feels normal. Could this have just been because they were hot, or is it time for a master cylinder? I do want to replace the brake hoses, and the battery and battery box this payday. If this needs a new master I will throw that on as well.

This is a 1967 C30 with SBC and Manual Brakes.