As a matter of fact I just remembered where it was. It measures about 3 3/8 horizontally and 3 1/2 vertically on the bolt centers. just throwing a tape measure to it. nd the aluminum is about 1/2 thick. I still have the aluminum master cylinder with 15/16 bore also. I ran it for a short period of time when I had a 93' cab with stepside bed stroker big block. I had to ditch the power booster to clear the valve cover. I made this around the year 2000. i dont think you can buy them anywhere
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