differences in hydroboosters

[69K5]

i have collected 2 hydroboosters.

one is chevrolet but im not sure what its off of. the second is of a 91 2wd (IIRC) it has a longer pushrod from the pedal and a gold canister on the inboard side that says compressed air. i guess b/c you cant compress a liquid. the older one doesnt have this. which one do i need?? the mounting bracket swaps between the two for the blazer.

there are pics of both in my webshots under parts.

thanks for the help

69k5 webshots

 

[R72K5]

looks like same rod as what was on a 76 1 ton hydroboost i removed

 

[69K5]

the longer rod or the shorter one. and which do i need?

 

[69K5]

bump need some help here please!