Regarding the weird master cylinder on the 55 Chryslers... This unit (power brakes) was for 1 year only and impossible to find parts for. But, Power Brake Exchange in San Jose will rebuild them for $238.00. I've located a complete master cylinder/booster unit off of a 55 Imperial that I will send to them. I'll swap it out with my existing unit when I get it back. As it turns out, the brake lock up problem was in the master cylinder return valve. This is a very strange design that seems to use two concentric pistons, one to take up the "slack" and one to apply force to the wheel cylinders. Anyway, thanks again to all the help replays I received. If you're going to switch to silicone brake fluid, you MUST clean out the entire system of old fluid. On to the next project.... Frank