John - There's one other possibility that may be involved. The below screenshot is from a 1947 Chevy Truck Shop Manual, which is still applicable in your case as the Huck brake system remains the same. There is a possibility that your master cylinder has an obstruction in the compensating port which is preventing fluid return to the main cylinder.
Dan, I don't want to label you a "Genius" until after testing. But, I got my MC on the bench and noticed the bypass hole is completely plugged. I didn't even know there was another hole in there. I took a pick and opened it up. I just got it installed, so I'll go around to each corner and adjust the brakes from scratch. Then I'll get the brake lines bled and try another test drive.
I'm hoping this was the issue - and it probably was. Thanks for all the suggestions guys!
