Can anyone tell me the size of the large hole needed in a bulkhead to take a Sierra Master Cylinder, also what are the spacings between the bolt holes to mount the cylinder. Thanks in advance

there are at least 2 different types; pretty sure they are not intechangeable.

I have one type that I can provide info. if you want.

There are 4 types, 3 cast and 1 drawn tubular one. The tubular one has a bolt patern the same as the pedal box so you can simply remove the servo and bolt back up again. Not so with the cast varieties.

There are at least 6 different types of Sierra brake master cylinders. 3 Girling and 3 Bendix.

Phil