But that got me thinking, I may have let some air into the system at the master cylinder so I'm going to bleed the rear brakes tomorrow just in case. While looking at the rest of the brake lines, I see a lot going on that I don't understand. Here's some pics. See anything unusual? I see a small distribution block on the frame next to the driver side front wheel. Then some other thing on the inside of the frame a little behind the same wheel. What is that for?
You have some shit going on.
The second picture is the factory proportioning/residual pressure valve. If you're keeping the factory rear drums, you want to keep that.
The other two pictures appear to detail some fuckery. The first looks like somebody spliced in an adjustable proportioning valve, and the third makes it appear they cut that aftermarket prop valve in in after the factory proportioning valve, effectively bypassing it.
Which might be the problem. Drum brakes require about 10psi of residual pressure be maintained in the line, or the springs in the drum assembly pull the shoes away from the drum. That leads to a soft initial pedal as the first hit on the brakes pushes the shoes back against the drum. The factory prop valve does this, but what I'm seeing indicates that valve has been bypassed.
In situations like this, it's always wise to get it back to stock and working properly before moving ahead.