Does anyone know if the 15/16” 280ZX brake master cylinder is supposed to have a dust boot here:

That collar is 38mm. The only ones I can find that look right are 26mm.

It looks like there’s a groove to hold one on, and there’s clearly a channel for an o-ring, but I can’t find one in the exploded diagram. I have seen a bunch of aftermarket ones that have a dust boot, including the Wilwood 1” MC, but nothing for the factory ones.

My aftermarket did not include one or referenced it. That might be a Wilwood exclusive. Personally you wouldn’t know when the rear seal is going bad. Probably would drain inside the booster IMO

I’m guessing no one has problems with that then. Maybe the clue is in the name (dust cover) and it’s more about keeping things out than keeping things in.

I have dealt with dust boots on master cylinders like that in other applications and have sometimes had troubles getting them to fit through the hole in the firewall. Not sure if that's because they had swelled over time or if they were poor fitting aftermarket items.

Bottom line? Maybe measure the hole in the firewall and see if you even have room for a boot in there before you scour the universe looking for one?