This high quality kit has a will really improve your brake performance. The booster mounts with a 4-bolt pattern. The 4 bolts are in a perfect square and are 3 3/8" apart (center to center).
1955 - 1964 Chevy Full Size Car 7" Dual Zinc Power Brake Booster & Bracket Kit
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Disc Brake Kit For 1955-64 Chevy Full Size Impala Bel Air Car Deluxe, 5 x 4-3/4"
For 1955-64 Chevy Full Size Impala Bel Air Car Deluxe Disc Brake Kit, 5 x 4-3/4"