Mocking Up Firewall for Master Cylinder Studs

I took these measurements off the 67 parts body as accurately as I can. You should be able to just lay these out on your welded in plate with a pair of dividers

The secondary measuring points are

The edge of the bulkhead connector hole as a secondary check From the edge of the bulkhead connector hole to the top left master cyl (MC) is 2 5/8"

The far right mounting boss as pointed out in the photo just above the inner fender bend
From that hole to the top right MC hole is 4 1/8"

The main points to use for measurement were the two upper bolts for the steering column plate and the upper right accelerator pedal mount hole as pointed out in the photo

TOP LEFT MC
From left steering plate hole, 5 3/8,
from right steering plate hole, 5 7/8


3 1/2 from top right accel pedal hole

2 5/8 from right edge of bulkhead connector hole

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TOP RIGHT MC

from left steering plate hole, 7 1/2
from right steering plate, 4 9/16
from far right bulkhead hole, 4 1/8

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BOTTOM LEFT MC

From left steering plate, 4"
from right steering plate, 4 5/8
From top right accel hole, 2 7/8

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BOTTOM RIGHT MC

From left steering plate, 6 1/2
from right steering plate, 2 3/4

Bottom MC holes are 1 7/8 vertically on center from top MC

all 4 are 3 /1/4" horiz. centers