First of all, what a beautiful truck.
It sounds like the brakes need to be adjusted. Older vehicles didn't have self-adjusting brakes. So, as the brake pads wore down, the distance of travel from released to pressed against the drum was longer, causing the pedal to sink down farther before the brakes would engage. Unless the brake pedal feels spongy (in other words, not resistant when stepping on it) after the brakes engage, it's possible they don't need bleeding. Read this.
How to adjust drum brakesIt does sound like something is wrong with the left front brake, so you should probably inspect that by removing the drum.