Difference between the 76' and 77' Brake booster?

[caribbee]

Does anyone know the difference between the 76' and 77' brake boosters? They have different part numbers. I have both but have to decide which one is best to use on my 77'. They both fit but just dont know why they have different part numbers.

 

[Artsvette73]

It has someting to do with the push rod for the master cylinder that I know of. Maybe more

 

[caribbee]

Ok thanks i will look into it.