Power to manual. 66 brake rod for 71 swinger?

Not sure what you are asking. The single reservoir can't be used on your car so I am wondering if you just want the rod? Removing it could damage the retaining rubber/nylon washer. Why not source an adjustable rod so there is no issue of fit?
The current MC used on power brakes is likely sized too big, either 1 1/16 or 1 1/32 cylinder, to be used manually. The pedal feel will be too firm to use everyday.