I've just started a disc brake conversion on my manual drum brake 67 bird using the system from SSBC. the only thing I am unsure about is the positioning of the proportioning valve. the instructions say to put the valve in after the stock metering block. Does that mean it goes between the metering block and the master cylinder? Any photos would be great.
Then you would put it after the factory distribution block on the 1/4" line that runs to the back of the car. I have done plenty of these swaps. Check the clearance on the front dust shields to the lower control arms. Some kits are stamped wrong and you have to trim the dust shield.
Chances are if you had drum brakes then you have a one piece brake line running from the dist block to the back of the car. In this case you probably should just replace that line with a two piece and mount your adj prop valve where the two come together. I mounted mine in the stock valve location under the floor below the driver's seat area. I can post a pic if you need it.