Wheel cylinder?

[cj55]

Trying to I.D. a rear axle for a 74 Chevy pick-up and whether it is 2WD or 4x4. It is on my 55 chevy truck. The brakes that were on the axle are 2-3/4" wide. The wheel cylinder bore size is 15/16" with the rubber boot on the outside of the bore and the pins have a tapered end. In trying to find replacements, the stores have a 15/16" bore with boot on the inside of the bore. The wheel cylinder for a 2" brake with a 1" bore has the boot on the outside of the cylinder. Which is correct? Help!!!!

 

[Pontiac1976]

Can you see if there any other info readable on the housing. I know that 75 and up to 77 there could be two different set up dependes on the option they hadon it. It is a 12 bolt right?

 

[cj55]

It is a 12-bolt. I cannot find any other id marks on it. I have tried finding them before - no luck. The axle has been painted with POR-15. Would it be ok to use 1" bore cylinders with 2-3/4" brakes?