So the new brake hoses are in, they helped quite a bit. Now that the pedal feels firm, I realized that there was quite a bit of free play. So I pulled the master cylinder off and adjusted the booster pushrod out.

That adjustment helped even more, but the brakes still didn't quite feel like I wanted them to.

In my mind, swapping out random components seemed like the best option. So I pulled the check valve out of my old booster and swapped it with the one on the truck.

It didn't seem to change much, until I tried pumping up the brakes with the truck running... It finally feels like I have a brake booster. I'm guessing that the check valve wasn't holding vacuum in the booster before, but now as long as I pump up the booster the brakes actually work decently.

I probably should get a new booster eventually, and maybe rebuild or replace the master cylinder and front calipers, but I'm totally ok with it the way it is. I got it to work, maybe not the way it technically should work, but it works nonetheless.

Oh, and I was wondering if the load sensing valve over the rear axle should be bled, and if so how would one go about doing that?