Yes, this is my first post - I've been a lurker for a while. I own a '55 6400 and fought the dreaded need to pump the brake pedal, despite new hoses, lines, MC, and wheel cylinders. Everything adjusted properly. Then it came to me!
I installed a Willwood 10 psi residual pressure valve in the brake line right as it comes out of the master cylinder. Part #260-3279. It holds the fluid in the wheel cylinders and doesn't allow it to bleed back into the master cylinder so you don't have to pump the pedal. One round of bleeding after the install and I get a firm pedal - first pump!
I have no affiliation with Wilwood. Here's the part:
http://www.wilwood.com/Search/PartNoSearch.aspx?q=260-3279
Best $30 I ever spent on the truck!!!
