proportioning valve... bad ?

[sactoC10]

OK,

The more I think about it, the more I realize that there are three areas that could be causing my brakes to stick...

Screwed up-old and deteriorating brake lines (maybe this is it).

Bad master cylinder (but I don't think so).

Screwed up proportioning valve (leaning more this way).

Here's my problem. I have new spindles, new pads, new fluid and yet the first couple stops are fine, but the following ones get worse and worse until both front brakes feel VERY tight. If the truck sits for a while, the brakes will be fine for another 2-3 presses of the pedal... then everything is stiff again.

What are the thoughts out there, proportioning valve, or lines?

JT