Hot Rods Power Brake Booster Hole Pattern

Hello All:
I'm posting for a friend of mine named Dave. His question follows:

"I have a 1964 c 10 with a power brake set up with an 11" booster I need to replace the booster. Trouble is all I can find have 3 1/2" center to center spacing to bolt to the firewall bracket. My booster has 3 3/4" center to center bolts. Is this a real old booster?"

"Is there any place I can find a booster that has 3 3/4" spacing? "

 

have a pic to post? aftermarket unit?

 

Elongate The holes.

 

JJ:
Dave says it's not an aftermarket brake booster.

He gave me three pictures. I'm not sure how to post pictures, but let's see if
this works.