Identical-looking brake boosters... what's the difference?

[Grec]

I'm noticing that brake boosters, the banded Midland-Ross for instance, have specific Mopar part #s with very specific applications.

My question is... what's the difference between two identical-looking boosters? I'm going to assume that the front and rear bolt patterns are all the same, especially when were talking about boosters for cars in the same model year, so what could be different?

Did they come with the car-specific backing plates... or is it a difference in the pushrod?

[dfrazz]

Some are made for drums only.  For example, my '68 Charger's original PB was only for power drums so I had to get a new one for discs.  I believe this has to do with the dual diaphragm.

[Grec]

Yeah... but say that the applications are both for disc/drum combos.

I'm asking this because I've come across a beautiful NOS unit that looks like a dead ringer of the banded Midland Ross unit in my car. But it says its for different cars.

[1 Wild R/T]

There are some different pushrod designs, there are strangely enough different bolt patterns on the firewall side...There are also different levels of asset within the same booster design...  But there are also some that the manual say is wrong that work fine... So if the price is right I'd consider taking the gamble...

[Grec]

Yeah. That's what I'm thinking...