Without ABS you should be able to lock all four wheels on dry pavement in a "panic" stop. It should be difficult to lock the rear brakes. You do not want the rears to lock first as the back then wants to pass the front.
Brake pressure is a finction of the pedal ratio and booster multiplication. Frequently the balance or bias valve is to reduce rear pressure preventing rear lockup. Drum diameter and widyh or rotor diameter and pad diameter work in conjunction with piston bore diameters to create brake torque or force. The master cylinder diameter converts the pedal force to line pressure. Wheel cylinder area converts the pressure to pounds force.
Standard accepted on our old cars is that under braking with weight transfer, the fronts do 70% of the breaking, on average. The front wheel drive cars shift that to 80% to 95%. Rear engine cars with more weight at the rear shift this closer to 50% to 60%.
In your case you should be able to lock the fronts but not quite the rears. Modern tires have considerably more grip than the skinny bias plys when these cars were new, which combined with wider tires creates more force on the brake surface to lock them.
You need to compare front and rear line pressures out of the differential valve and multiply by the piston area of the caliper. This will give the force applied to the drum or disc. Once. You know the line pressures I would talk to the component supplier for advice.
