1987 Cherokee Brakes deep concern

I recently replaced the brake system in my truck.From the master cylinder-and-booster to the calipers and weels cylinders. I even did the rear lines 'cause they were rosted and about to brake. Brake pads and shoes, hoses, everything except for the "pressure differential valve" or "compensation valve" I know she is not stoping well, it has NO ABS, therefore it should lock the weels if I press hard enough on the brake pedal, right??? Well, she's not. I wonder if there is air still in the system or if i should also replace the valve. AH AH, it was doing the same thing (kind of hard to stop) before all this work. I've also heard that I could use a valve from a "Liberty" or so since the original one can only be found at a dealer and it costs.........$$100+++.This realy worries me. Any suggestions? Thanks

Yes, make sure you bleed the entire system thoroughly. Once you've done that, let us know if the problem continues.