heres what you need.... the booster, booster to firewall brackets, and the pedal rod... go look for a 67-70 c10 or c20 (try to find a 3/4 or bigger truck because they have a bigger better booster) and while your at the junkyard might as well take the booster to... pull it off as one complete assembly should run you about 50 bucks
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www.xframeimpala.com
68 4x4 short fleetside deluxe cab 327 air
56 big window short stepside 235 dual 1 brls
64ImpalaSS 327
70 C10 LWB fleetside custom/10 350/TH350