My 70 has a booster that looks like that, and it was also installed in LA back in late 90’s. After 25 years, it’s no doubt end of life and I have a rebuilt correct Bendix and new master cylinder ready to swap in. Of course while I’m at it, the brake warning switch needs rebuilt, and the rear brake hose replaced, and….
I ended up getting one from NAPA that fit. Not sure if it will help until I finish the exhaust and that won’t happen for a few more weeks when the downpipes are delivered. I MAY be finally driving this Cat in June. I still have to go through the setups and tuning for the FiTech. (I also saw my power steering ram is leaking so that’s on the list)
I still worry if I have enough vacuum for the brakes and transmission with this setup. I’m think there is the possibility that I’ll have to install an electric vacuum pump.