2" or 2 1/2"- the only way to really know is to remove one front and one rear wheel. Dual M/C- I don't see the need as you only have the small 9" brakes, not worth the trouble. I would stick to the original setup.
are you serious? that is some of the stupidest logic I have ever heard. that is one of the first upgrades that should be done to these old cars. one line goes out and No brakes.... dual master one line goes out and you will still have some brakes.
