whynot sent me some pics of his setup, I'll post them here. There was a couple of pictures of the mentioned 2 piston calipers, but as they were not mounted on the car, I left it out. ( I don't recognize them, but they look like fronts to me.)
One of the problems lies in the fact that those wilwood calipers in the front need alot of pressure to work, and are designed to use a small master cylinder, while the rear calipers have a great deal more piston area, and require a bunch of volume and pressure to work..even when adjusted...so they need a larger master cylinder...That's why folks have a problem with the front /rear brake bias when they run the lincoln brakes on the rear... The last car I straightened out with the Lincoln Versaille rear brakes and small piston front calipers out had a similar setup, and would not make the 1300 psi line pressure required by the fronts without the addition of a hydroboost and a 1 1/8" master cylinder and a proportioning valve. With that setup the system made 1500 psi line pressure at the calipers with the pedal about 1/2 way down. I'm sure that car will stop, but as it is still not been road tested I don't know if the rears will still lock up before the fronts, even with a propvalve....
IIRC the Lincoln Versaille used a smaller rear piston caliper than the Mark IV, but those too were a problem when used with small capacity front calipers. I know a couple of road racer guys who said they would have the Versaille calipers resleeved and run a pinto front piston in them to get the bias right when they ran with the early 4 piston mustang calipers...but it proved to be too much hassle.
You still need to tell us if the pedal is hard, with no stopping power, or if it goes to the floor without being able to stop the car...from your pedal measurements it appears that you have a 3.3:1 pedal ratio, which, if the pedal is 5 or so inches from the floor, would give you about 1.5 " of pushrod travel, which is more than enough to utilize the entire stroke of the master cylinder and deliver plenty of volume.......but the 7" booster gives very little assist, even if the vacuum is 20"...I have plumbed brake boosters into the base plate of carbs mounted on blowers, and gotten great vacuum....A high hard pedal tells us that you have enough volume, but not enough assist, while a low easy pedal can mean a number of things.
I have found that plumbing a high pressure gauge into the bleeder port on a front caliper is an invaluable diagnostic tool on mismatched brake systems. The pressure requirements at the front are the greatest, and if you can't get 1300 psi at the fronts, either because you run out of volume, or assist, the car isn't going to stop well.
Another thing you might consider is that the pads are clogged with rust from cleaning off those rotors...
my signature lines...not really directed at anyone in particular..
BE different....ACT normal.
No one is completely useless..They can always be used as a bad example