poorboy, what size is the master cylinder bore ? the wagner book i have shows most corvettes have a 7/8 or 11/16 bore. this should be ok for your application. is it possible your rear flexline[rubber hose] mite be partially collapsed ? i would be concerned about that firewall flex. also, i agree with rodstrace you should remove the proportioning valve & see what happens. is there any possibility of binding in any of the pedal assembly ? brakes can be a real pain sometimes...........