Brake booster leaking in 77 M880

Getting ready to purchase another brake booster to replace the one on my truck. Any difference than the W200 brake booster for the same year, or do I need to be looking for a different one?

TIA

Should be correct. But I have no verification of that.

bwhite, have you found a source for a replacement brake booster?

Does the Brake Booster on the M880 need a gasket between firewall and BB and MC and BB? Installed a spare I had and saw remains of gaskets on each location.

I didn't put gaskets back (didn't have any and couldn't see the need for it) but having a hiss when brake pedal is depressed. MC has been bench bled but not wheel cylinders yet.

Check valve is fine and no vacuum leaks...well, not if the hiss is a vacuum leak.