Here is what Fred wrote for the Master Cylinder conversion:

Hi, I wanted to share some of what I have learned about the process of converting the single reservoir master cylinder in my 1964 Crown to a dual reservoir MC.

I completed this yesterday after a fair amount of thought and research. I have not completely finished the process yet, (bleeding etc.) but will share what I have done so far.

The dual reservoir master cylinder that I used is spec'd for a 1967 C-Body. It bolts right on. I have not adjusted the brake push rod and it looks like I will not have to.

I was going to use the distribution block that I acquired from a 1967 Fury with all drums. Note that this distribution block is exactly the same as in my 1969 Imperial with Budd discs if anyone is ever looking for one for their Imperial. I use the term distribution block and not proportioning valve because that is what it is. It is basically two separate distribution blocks in one body. There is one port in with two ports out for the front brakes and one port in with one port out for the rear brake line. There is no crossover between the front and rear circuits.

Then on Saturday night I had an epiphany. I could use the distribution block that was already in my 64 Crown for the front brake circuit and connect the line from the rear brakes directly to the master cylinder. This would make for much easier and tidier brake lines and with no compromise in function.

This is what I did for the brake line plumbing:

A 9/16" to 3/16" brake line adapter (ca 6" long from NAPA; $8) was connected to the front outlet of the master cylinder and then connected directly to the rear brake line using a 3/16" coupler. You need about a 100 degree bend in the adapter line about 2" out from the 9/16" fitting and then bend the original metal rear brake line up to meet the end.

A 1/2" to 3/16" brake line adapter (ca 6" long from NAPA; $4) was connected to the outlet of the MC nearest the firewall. You need a similar 100 degree bend in this line. It was then connected to a 20" 3/16" to 3/16" piece of straight metal brake line ($5 O'Reilly's) using a 3/16" to 3/16" coupler. This was then bent to make a connection to the 3/16" port of the OEM distribution block that had originally had the rear line exiting from it. The brake line drops vertically from the MC and follows the frame rail to the distribution block. I fee that this is a better route that the original design which is quite exposed and goes into the top of the distribution block. You then need a 1/4" plug ($3 O'Reilly's) to plug the port on the distribution block that was originally connected to the single reservoir master cylinder. I bought the couplers at a local agricultural supply store for about $1 each but they should be readily available.

If you do it this way you do not even have to loosen the metal lines to the front brakes and the parts cost about $20 plus the new master cylinder. Tough to beat!

You need to remove the battery tray and it really helps to remove the power steering return hose (or hoses in my case if you have the power steering cooler).

This install was made possible by the availability of the brake line adapters at NAPA which I did not discover until Saturday. Getting 3/16" brake lines with 9/16" and 1/2" connectors is not trivial unless you make your own but the adapters are better in my opinion. You do need to insert couplers in the lines and use a plug but that is not a problem.