Proportioning Valve

You may have several problems, so don't lose hope.
The lack of a Proportioning valve, like Del says is Not your biggest problem at this time. I have no P-valve on my combo, but I do have 295/50-15 tires on the back with very small wheel cylinders.
If you have four same-sized tires on your car, you will have to get some kind of reduction-system in the rear lines, no matter what, or suffer spin-outs on a regular basis with heavy brake application.
But that is not your current problem.
You have two or three current problems;
1) the low pedal and
2) the high required pressure, and
3) probably a spongy pedal.
4) and possibly you may not be aware that disc brakes are NOT self-energizing like the drum brakes were, so will require a great deal more leg power, unless you have installed a power booster.

Ok so lets look at these one by one;
but first, a few questions;
1) Do you have a booster?
2) did you bench-bleed the master?
3) To which end of the car, did you plumb the front reservoir?
4) What is the size of the master cylinder bore?
5) why did you install the calipers to the front?
6) are the calipers actually free-floating?
7) and as already asked; are the bleeders at the highest points of the calipers?
8) does the pedal come up higher with multiple pumps?
9) do multiple pumps make the pedal harder?
for 8 and 9, you have to stroke faster than the fluid is able to return, but the pedal has to come all the way back up to the top each time.
10) with the system fully relaxed, have a helper slowly apply the brake pedal about one inch then allow the pedal to very slowly return to the top of it's stroke; while you are looking into the reservoirs with a flashlight.. You should see the fluid roiling from the Compensating ports, right during the top inch of pedal travel in BOTH directions.
BE WARNED;
If your helper pushes more than an inch AND if there is air in the system, then it is possible to get a fountain on the upstroke as the fluid returns to the reservoir. I have seen gusher-fountains erupt and hit the underside of the hood. Brake fluid is not paint friendly, so if this happens to you, you gotta have the cleaning supplies, including some Brakleen, right there. I will not buy you a new paintjob..
This test is very important to proving that your M/C pushrod is properly engaged and adjusted to the correct length.