Which Brake Booster??? Help!!

I have a 1969 dodge dart. Doing a S6 to V8 Conversion.
Doing a front dist brake conversion and have 10" rear drums. All 4 on 5 bolt pattern.
360 with a 727 behind it.
So,
I want power brakes and need to know which diameter brake booster to buy. I heard the larger 8" boosters are impeded by the valve covers in the engine compartment. True?
I have found some decent deals on ebay but maybe someone has a booster/master combo I can buy?
Also I need a new front proportioning valve. Any ideas/have one I can buy?

New at this and need a little help.
Thanks!!!!!