New member, need advice - brakes

[ChromeDome Al]

Hello from your redneck brethren in Montana! I acquired a '70 K10 LWB (which was apparently dubbed Optimus by a previous owner) a few years ago when I lived in WA. It has a built 396 (w/ a wild cam), Edelbrock 750cfm, Flowmaster 40's, a 6-inch Skyjacker/Bilstein lift, 35-inch mudders, eats Priuses, and breathes fire. The body is straight, and sounds like there isn't any mud in the panels, but it wasn't blocked out when it was repainted (I'm guessing 10 - 15 years ago). The interior ain't worth a Thai hooker, but she gets down the road alright. Wait a sec...no, I take that back. She has some wicked gearing - Like 5.28's or something. I'm in 3rd before I leave the parking lot. No joke. Top speed - 45 mph, grandma style. I couldn't get a speeding ticket even if I wanted.

So, on to the main purpose of this post - my brakes. But a disclaimer first: I'm a self-taught, young, impressionable mechanic. I learned to turn a wrench on my '63 Pontiac Tempest and my '07 Subaru Outback XT (a turbo'd grocery-getter that knocks the socks off of hairy granola mommies.) Any future claims of stupidity are valid - I don't know what I'm doing. I have a basic understanding and knowledge of vehicles (because of youtube) and I have about 6 tools (which aren't actually mine). But I love to tinker, so let's get on with it.

I just dug the pickup out of storage in WA and brought it to MT on a flatbed. After getting it started, fighting the shift linkage, and re-installing the column, I figured out the truck REALLY wants to go, but it doesn't want to stop. I was sure there was condensation in the lines, so I bled the brakes. The fronts had a mega-strong stream out of the bleeder valves, while the rears had more of a dribble. I bought the pickup as it is now - disc front/drum rear. Also, the booster appears to be newer. The brakes have barely enough power to stop the truck from a rolling start. So they're engaging, but not very well.

I've ruled out all issues with hardware (such as pads, calipers, discs, shoes, drums). So...what are my options with the brakes? How can I tell that the master is good? Could it just be a proportioning valve issue? I assume there is no holes in the hard-lines because there aren't any drips, but is it possible there's not enough pressure to force some air out? Also, with a wicked lope on the cam, is it stealing too much vacuum from the booster? (Hopefully, my pictures have posted. this is my first time using a server-based photo sharing system.) Check out my pictures and see if the hardware gives you any clues, (such as, "hey, the ass-hat who put discs on that truck didn't put the right master on!" or any relevant notions.

Thanks for any and all input! Back to pretending like I'm working.