-you can run the correct master for your 80 camaro front clip as long as you get the one for disc/disc application and it will bolt up to your booster. you would mount it on the frame mounted booster like usual and probably run some valves inline, called residual valves, to hold a 2 lb pressure in the system. some master cylinders have them built in but more or less just the ones built for drum brake applications. this is to keep the fluid from running all back into the master cyl when the brakes are released because the master cylinder is quite a bit lower than when firewall mounted. when that happens it takes a bunch of pedal movement on the next brake application in order to fill the system back up again and usually results in a spongy pedal.
here is a quick explanation.
https://www.freeasestudyguides.com/r...eck-valve.html
and an idea for pricing
http://www.jegs.com/p/JEGS-Performan...48183/10002/-1
you may also require an adjustable proportioning valve to regulate how much brake bias you have. brake bias is how muich front brake you get compared to rear brake. this is so you don't skid the rear wheels every time you hit the brakes.
here is an explanation from a super chevy article
http://www.superchevy.com/how-to/713...tioning-valve/
-you will probably want a dual diaphragm brake booster in order to have decent power assist and still be able to have room for other stuff, like exhaust pipes etc, under the floor area. another thought would be to install a hydroboost system from an astro van or 1/2 ton that would give you awesome power assist and take up waaay less space. you would need a power steering pump that has 2 return ports or else do some creative plumbing. check ogre's build to see what he has done, or send him a pm and maybe he can send you a couple of pics. if you google hydroboost you will see it is not that complicated to figure out.
below is a link with some pics of the vac booster so you can see how much room it takes and how it looks generally.
http://67-72chevytrucks.com/vboard/s...d.php?t=523434
below is a link to this site where guys have built their own version of hydroboost for the 55-59 trucks. you could pm then individually for more info and pics. read the whole thing for talk about master cyl choices, pedal ratios etc
http://67-72chevytrucks.com/vboard/s...d.php?t=498494
below is a link to POL's version with pricing for a kit but it also has a pic so you can see what it would look like. there are guys on this site who have done their own and it was likely cheaper. not sure on what you have for fabrication skills and tools.
https://www.performanceonline.com/19...e-Booster-Kit/
-you will probably be needing to replace the old rotors and pads and possibly the calipers due to age and possibly sticky or seized caliper pistons. you may also want to bend you brake hoses sharply and check for any cracking of the rubber hose and also give them a little tug to check for stretch. you don't wanna do all that work and then blow a brake hose and crash. hoses are pretty cheap really and easy to do when your system is apart anyway. when purchasing the rotors look for the ones that are coated or painted on the non brake surfaces. the other raw steel ones will rust and make a mess on your wheels all the time. unless you paint them first.
-you may want to at least check the front end suspension parts for wear before you get anything else assembled. it is easier to do that work without a truck body sitting on top of the frame. parts for that front end will be fairly cheap as well but price it all out and go from there. it is better to start with a good base under your truck than to get a bunch of other work done and then have to go back and take it apart to fix some loose steering items. if you do it all properly the first time it is less expensive overall and you have peace of mind as well with no hidden last minute expenses like when you take it for alignment and the guy calls and says he can't do it without new ball joints or whatever.
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