[HO455]

Hydraulic systems like brake systems are a master cylinder that moves a specific volume of fluid per stroke of the piston. The amount of pressure is determined by the amount of force applied to the piston. The pressure is applied equally throughout the inside of the tubing and slave cylinders (and any other components installed). So the size of the tubing doesn't affect the pressure of the system, as long as the piston can supply enough fluid per stroke. (Too long of tubing or too large will limit the pressure capacity of the system.) In a brake system like ours there are two pistons supplying two sets of tubing and two sets of slave cylinders. (Calipers are slave cylinders just configured differently). In a perfect system where both pistons are the same size, and the slaves are the same size, when you move the pistons (at the same time). The slaves will react exactly the same. Same amount of movement and same pressure at exactly the same time.
If you redesign one of the two systems and give it slightly larger tubing and repeat the test. The side with the larger tubing will have the same amount of movement, at the same pressure, but it will be slightly delay when compared to the other system.
Thus if this is our truck in stock condition when you step on the brakes the rear slaves will always be applied slightly after the front slaves are applied. Now you could get the same results from a properly engineered brake proportioning valve, but GM is cheap and the cost of a one size step up in tubing versus a properly engineered proportioning valve was a no brainier for them back in the day.
For your application you can run the same size tubing for the rear as the front but you may want to install a adjustable proportioning valve in the line to the rear brakes to slow the speed at which the rear brakes are applied. Now you may not find that you have an issue with how your brakes work without an adjustable proportioning valve. But the day may come when you're on a wet corner at speed and have to tap the brakes and suddenly find that your rears have locked up!
As always your results may vary.