70 cuda power brakes are too sensitive

I just finish putting my 1970 AAR Cuda together. The car was not complete when I purchase it. It had the brake and clutch pedals with the main bracket. I picked up a used brake booster, reman master cylinder, used swivel assembly, used brake switch valve, metering valve, and proportioning valve. If you push a little too hard, the brakes will lock up. Causing the tires to squeal.
Author: gary