I believe that the plug marked by the arrow in the attached pic could be removed and a brake line connected there. That would do away with the funky short line and tee hanging out in space.
IIRC '54 and '55 trucks used that spot for a line to the left front wheel with the other line going straight out of the MC over to the right side frame rail and a tee to the right front wheel and to the rear axle (both wheels). The earlier trucks (my '51 included) used a single line from the MC to a tee on the right frame rail and another tee at the RF wheel branching over to the LF wheel across the front crossmember.
[on edit]It looks like the '57s would have the same configuration. The second picture is a composite from the 1929-1957 Chevrolet Parts and Accessories Manual. It show the brake diagram and the 1957 brake line lengths. I believe the GMCs would be the same.
Last edited by klhansen; 10/03/20252:54 AM. Reason: added more info & picture
Kevin 1951 Chevy 3100 work truck Follow this saga in Project Journal Photos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together.
