No you do not need to run the prop valve, unless you want the brake warning light to function due to loss of brake fluid pressure. I always thought that was obvious and you don't need a light telling you so?
I have a similar setup (less expensive) setup in my chevelle. 05 Tahoe hyrdoboost, 80's corvette master cylinder (disc/disc, 1 1/8" bore), LS1 fbody disc brakes.
I have the front line running to a line lock / roll control valve and split going to the front brakes. Rear I have wilwood adjustable prop valve 260-8419 mounted to the same bolt as the master cylinder than a 3/16" nicop line running to the rears. 15k hard miles on it so far with 0 issues.
