Hi, Paul,
My P.B. booster has the following measurements:
On back (bolts to firewall bracket): 94mm CtoC horizontally, both top & bottom
On back (bolts to firewall bracket): 89mm CtoC vertically, both sides
So, the rear bolt pattern is a perfect rectangle, with 90 deg. corners.
On front (attaches to M.C.): 82.5mm CtoC horizontally, both top & bottom
On front (attaches to M.C.): 45mm CtoC vertically, both sides
The front bolt pattern is also a perfect rectangle, with 90 deg corners.
Hopefully, this isn't clear as mud. Let me know if it is.
Also, you may need a new check valve. The one I bought is on ebay and is made for Studebaker's Bendix P.B. booster by Fusick. $28.50 + shpg.
Regards,
--Dwight