OldIHC

First time posting..Start off by saying thanks. My build (project) 1948 KB 6 welding rig
The truck runs great...stops not so good..Just bought rear wheel cylinders. Need the find
Front wheel cylinders...

Check in the: Re: Parts Link Format
Type in " Wheel Cylinders" will find some info that might help you.

My experience with the larger K's (-6 and up) is they have excellent brakes. I have 2 -7's and one has a lighter GVW (closer to what your-6 would have) and even at 18K gross, it had no problem stopping.
Unless your truck doesn't have a Hydrovac, woah power shouldn't be a problem.
Rear cyl are the hard ones, fronts can easily be sleeved and rebuilt.

Thanks for you're reply. Really not sure about the hydrovac..it has air compressor. Air valve under the break petal that operates the master cylinder on the passenger side .It also has a trolley brake on the column.
....

Pictures always help.

air brakes , nice

I'd like to see pictures of this set up, Never seen a -6 on air and I thought -7's were the start of air being an option.
I'd have to double check my book, but I don't think they made air over hyd from the factory, it would be either all air or all hyd.
Trolley valves were made and used for vacuum as well as air (different unit but same idea)
Quite possable it was "converted" into a tractor at some point to pull air braked trailers. Right after the war trucks were in short supply and many hyd braked trucks underwent a conversion to pull air braked trailers. Kinds sounds like what you may have.
The large majority of the -7 were hyd braked and that goes for the -6's as well. -8 and -10's saw more air brakes but even then they aren't common.
I love to see pictures of what you have, it isn't everyday you see air on a lighter truck.