Brake booster rebuild kits.

Harmon Classic Brakes, I think this may be the best/only source? Note case size, they dont list a rebuild kit for a 67 BARRACUDA, but this is for a Dart. also core charge for 2 pieces.
http://www.parts123.com/parts123/yb...~S4OP0LR1J876951647770a~Z5Z5Z5~Z5Z5Z50001029z