This is a complete bolt in kit designed to work on 1968 & other year GM medium-duty trucks that gives a firewall-mounted Kodiak / Topkick style hydroboost booster and huge 2" bore master cylinder. It's important that you confirm fitment before ordering by comparing my pictures and measurements to your truck. There may be variations in these trucks I am not aware of. This kit is meant for trucks that have an original firewall booster with a 3.75" x 3.75" pattern. This kit does away with the oem parts and replaces them with a modern booster and master.
This will likely not be powerful enough for C70 and larger trucks. Those truck seem to have come with 12" dual diaphragm boosters and I expect this 11" system won't work well in their place. Measure your original frame booster. If 11" diameter, this system is a good fit. If 12" diameter, you probably won't be happy with this kit.
 
This does away with the slave system and under under-mounted booster. This booster installs in about an hour and requires no cutting or permanent modification. It works with your existing brake pedal and existing power steering pump. Kodiak hydroboost do not plumb in like other hydroboost you might be familiar with. You leave the existing high pressure hose that goes from pump to steering box. Add in a new high pressure hose (included) that runs from steering box to booster, then there is only one return line back to the pump.
 
For the brake line routing, you need to separate out two circuits to get the safety benefit of a dual circuit master. You can reuse all of the existing lines that are downstream of the original junction block.
 
Tag Axle
Trucks that have a second (tag) axle have a secondary brake booster and master cylinder that feeds the rear axle. Our firewall-mounted system does not replace this secondary system. We have limited experience with this. Please review that system before purchasing, but it can likely remain intact and operational with the modern brake booster serving the primary axle. Using the new master cylinder to serve two rear axles will cause an out-of-proportion system, and the front brakes will do all the work, with the rear brakes being hardly activated
 
Included parts with this kit:
Firewall booster brackets, painted black
Kodiak style hydroboost
Kodiak style 2" bore dual output master cylinder
12 volt backup pump and relay
High pressure hose and low pressure return line for hydroboost
6AN adapter fittings for high pressure plumbing
Custom bushing designed to mate SD booster eyelet to factory brake pedal
High quality grade 8 hardware for entire install
Flare adapter fittings- to connect standard 7/16" inverted flare fittings to the master cylinder (common on 1/4" lines)
 
These brackets are designed, laser cut, and formed right here in the USA. The parts supplied with them are top quality