In 1967 chevy started using the dual master cylinder in the G-10 Vans being produced. Please note that the early series Chevy and GMC Vans were the old flat nose vans and that the M/C was located under the floor board with pedal extending through the floor board like in your '38. After owning and playing with old straight axle Chevies for the past 45 years, I would think that the 67- 69 Van M/C maybe worth looking into. The cylinder bore is 1" and the M/C can be ordered through Advance Auto Parts either new or rebuilt. Check the bore size on your '38 M/C for compatability. If mounting holes are close enough, your in. Re-route front and rear brake lines to the correct outlet on the new M/C and drive safer,longer. You may have to modify the brake rod attached to your pedal assembly. Strictly a Chevy Nut !!!!!!!
