Just use DOT 3 brake fluid. Put some fluid in there, and have someone pump the brake pedal while you look under the truck for leaks. It's probably a a single MC setup. I know my '66 C-10 has a single MC. I would look for a leak in the lines somewhere, or a ruptured hose. What surface is the truck parked on? There should be some trace of a fluid leak. Good luck. John
1968 Chevy C-10, 250 and 3 speed on floor, Hedman headers, Offy intake, Edelbrock 600cfm 4 barrel, HEI
1966 Chevy C-10, motor and tranny went into the '68. Waiting to be restored.
| 
