Well just got through fitting a 9" brake booster and it's one hell of an improvement! So much so I will forget about fitting disc brakes for now.
67 Firebird 350, TH350 auto Convertible, B&M 3000 TC, 4bbl Edelbrock Performer carb and intake Black Jack headers,disc brake conversion. 10 bolt chevy axle with 3.73's and B&M Rachet shifter.