Converting my manual drum 67 B-body to PDB. Can I use the same brake metering block that is attached to the frame rail under the master cylinder? I know I need an additional metering block for under the drivers seat rail for the disc brakes. Thanks.

That's not a metering block that you have, it's just a distribution block. Yes, you can do like you said, you can keep it and add a proportioning valve for the back brakes. Don't forget that you also need a different master cylinder and all the stuff that goes with it and the booster. Also when you get done the pedal will be close to the floor and this is normal.

That maybe the case, but not the goal, care to explain?

It's may be, jcc. Not maybe. There is a difference.

Generally, the brake pedal for a manual brake system has the hole for the rod to the booster/master cylinder lower on the pedal then the hole is on a power brake pedal. The lower hole gives you more leverage for the manual brakes. On some cars, that lower hole will cause the pedal to sit closer to the floor when everything is at rest. How much closer to the floor really depends on the brake pedal itself and the car its installed into. Some cars the difference is noticeable where some other cars you can barely tell the difference. I'm sure the + or - tolerance of parts during that era Mopar also has an effect on weather or not you notice a difference in pedal height. The at rest pedal height does not have much effect on brake function (the rod to the booster/master has an adjustment to take up the any difference in pedal free play), only on the pedal height at rest, which might take some getting used to. Gene

So installed the PDB set up and sure enough the pedal is lower to the floor. I think there will be enough "pedal" for it to work fine, but most likely will not line up with the clutch pedal, but the car is still in restoration mode. The car is a 4-speed car and the above explanation makes a lot of sense. Given that, would it be safe to assume that a factory 4-spd car that was factory PDB would have the hole in the pedal higher? Thinking that maybe 4-spd pedals from a PDB would make the pedal higher.

the higher the hole for attaching the push rod to is to the pivot point, the bigger the pedal ratio is.
in other words, the high attaching hole is for manual brakes. think 6:1.
power brakes always have a lower ratio, think 4:1, therefore the hole is farther away from the pivot point of the pedal.

When you get your conversion kit, be careful where you get it. I bought one that was "for your car." It wasn't. I had to be creative when getting the brake lines to mate into the new master cylinder. Then years later I discovered I didn't have the right brake parts on the wheels. Searched all over to get real Mopar brake parts, and there were a couple of brackets that are not available aftermarket, so I had to find some from a junkyard. I never would have known if it weren't for Year One. I ordered a new brake hose from them thinking I had the correct parts. When it didn't fit, I thought they screwed up. They didn't. When I researched it I made the discovery. All Mopar now.