Options for 69

[Rustyrodknocker]

I have been tinkering with a 69 newport and I see that it has a different booster and master assembly than my 300. My 300 Is a dual diaphragm style while the newp in a single.
Can anyone shed some light on this? Maybe there is a heavy duty version?

 

[413]

Disc brakes had the dual diaphragm type.
Drum brakes had the smooth one that is clamped together.