I just wanted to throw this out there. I saw a post from years ago, I don't think it was from here but wanted to at least let everyone know of this. I needed fuel pressure at 24psi and there is no spring available or at least could not find one searching for days. The red spring goes from 18-22 and then the next spring is 28-32 aproxx.
If you need 2-3 extra psi you can get a rebuild kit for a rear wheel cylinder for a 1995 c1500. take the spring and put it in the fpr inside your spring you have it fits nicely and does not touch so no coil bind. put it back together.
I tested at a turn before maxed out and I was at a touch over 25psi. I am using the tpi fuel pump.
I lowered it to about 2/3 and I am at 24 now.
So instead of bigger injectors or fittings hoses and external fuel pressure regulator this can be an option for a couple of bucks.

Just wanted to throw this out there if you need just a little more.