Usually when I hear of a brake transplant that cannot be bled properly, the calipers are on the wrong side of the car.  On the 70 front disc calipers, the bleeder screw must point to the REAR of the car.  It seems logical to install the bleeders pointing straight up, but that is not the case.


You did not say what rear brakes you have.  It would help to have that information as well.
What booster are you using?  You mentioned 2000 Mustang V6 power brake upgrade, but I assume you mean the 2000 master cylinder, not the booster.  Drums or discs in the rear?
Did you perform the pedal pin modification exactly per the drawing?  Mispositioning the pin even a little bit can result in the pedal sitting way too low.

You would not be the first to make that mistake.  I think I was...

As for that booster, that is not one of the specified boosters for the kit, so I am wondering if there is a different rod length or something?  Or is is actually from a 79-93 Fox Mustang as specified?

On the rear drums, if they are not adjusted out against the drums, the pedal travel will be excessive with no braking action going on.  Adjust them tight against the drum, then back off ten clicks.

If the booster fit the plate supplied with the kit, and the booster was capable of being bolted to the firewall, then it is not the problem, unless the output shaft is not properly adjusted.  I should have mentioned that before... The output shaft of the booster needs to fit the master cylinder within about 0.010" of touching the piston. 

Since you have less mechanical advantage on the brake pedal, without any vacuum the pedal will be harder to push than if you have vacuum, but the travel will be the same, which should be about 1" to 1-1/2" total to achieve a fairly hard pedal.  The pedal might go a little farther than that, but you have to push real hard to do it.

The master cylinder is likely not the problem.  You are getting fluid to all four corners of the car, so it is flowing.  Did you bench bleed it?  Do you have any of the hard lines running ABOVE the level of the fluid in the master cylinder?  That can trap air.

What about the rear drums?  Are they adjusted tight?

And about the caliper positions... Did you check???????

It would be a shame to scrap parts that are perfectly fine.  Would you rather have a chinese booster with no pedal ratio correction?

It would be a huge help if you could post a picture of the booster/master cylinder/proportioning valve area and a picture of the calipers as installed.

Post a picture of what you have for booster, master and nearby tubing.

Last time I bled some 69 calipers, I had to get out the vacuum pump to get any flow.

How far off the floor is your brake pedal in static position?  Did you adjust booster output shaft.
I cannot help any more without a picture.

Any particular reason you went with that master cylinder?

If it works and you now have good brakes, then it must be good !