Thanks for the input, I payed attention driving home from the office because my 2500HD has hydroboost and the pedal only requires a small amount of travel for normal driving, I do like that.
Here is where I am at tonight:
I had hoped to not need a spacer so I mounted it with the Yukon backing plate, I like that it's flat or parallel to the ground but the proportioning valve is too low and probably close to exhaust manifold and the brake lines from the valve up to the mc are hitting the fender. The valve could be relocated and the lines bent to fit but there is more.
It may help the rod to pedal pin alignment if the assembly was tilted up a little. I believe I will try to use the Cherokee aluminum spacer that has some tilt built in.
And the snout of the hydroboost projects a bigly amount past the firewall.
Pedal up full travel,
Pedal down full travel,