reggiis - If you do end up replacing the existing units, please don't trash them. They are super hard to find and there are some folks that would love to snag them as there are still a few rebuilders around to get them back to proper operation. That goes for the vacuum booster, master cylinder and even the vacuum lines and fittings.
You can offer to sell or give them away in the appropriate
Swap Meet forum and help one or more fellow Big Bolters out.
