Since the original brake system is only single stage and has insufficient pedal pressure I decided to upgrade to a vacuum assist brake booster.  This consists of a conventional dual stage master cylinder, 7" vaccum cannister and a brake mounting system.  Unfortunately there isn't much out there that allows both brake and clutch pedals to work together as it seems most manufacturers seem to think everyone has a Hot Rod with an automatic tranny.

This is a 1937-38 brake booster mounting bracket that has been modified to use the original master cylinder, brake and clutch arms.  This product can be seen at:
http://www.piratejack.net/
http://www.mbmbrakeboosters.com/



Top view showing the brake adjusting rod going through the middle of the old master cylinder.  Refer to the top photo for attachment details.

Dual diaphragm brake booster system installed on original K member location.  Note for a drum/drum system you must use a 10 pound residual check valve on both front and rear lines.  You can also see the original hydraulic brake switch plumbed into the rear line.  Make sure you get a tee-fitting that use 1/8" pipe thread in the middle and flare fittings on the ends for the brake lines.

Front portion of original master cylinder brake arms attached to diaphragm rod for vacuum assist.  You have to make sure the original brake and clutch arms go back into their original locations.  There will be much messing around with the mounting bolts because there are only two mounting holes for the whole system.

Spend your time bending new lines (I used 3/16" instead of the original 1/4"), bleed the system carefully and adjust the pushrod length several times to make sure there isn't any preset to the brake pedal.

You need a minimum of 14" of vacuum to get the system to work, so check your vacuum at idle before you start.  Since the original Chevy brake system uses dual slave cylinders the car brakes like a modern car, plus it's much safer because of the dual reservoirs.