Help with Power Brakes '57 3100

[Dan87GT]

Hello....I am re-doing the brakes on my '57...it has been upgraded with a later style power brake booster, etc....I have 2 questions I was hoping someone could help me with....1) Any idea what this booster is off of?...It is marked Bendix 11869 but I cannot find a reference online....the truck has a custom brake pedal asm and I was was hoping for a direct replacement booster....bolt hole spacing is 3 1/4(width) and 3 1/2(height....2) When looking at replacement master cyl/brake booster I see that most have the proportioning valve mounted to the brake asm...mine is mounted low on my frame..does it matter?

thank you!!