master cylinder interchange

I was blown away when I went to the parts store here in town, and they had a master cyl and wheel cylinders I needed for my '59 American IN STOCK!  (I am talking the REAL parts store, not a "McParts" chain store where seat covers and air fresheners are the specialty).

I see some vehicles on that list that should be a dual cylinder. I'm new here can anyone point me to  any articles on upgrading to 10 inch brakes or other bolt ons?  I don't want to cut the car other then maybe enlarge a hole or something simple. 

Thanks

I changed from 9" to 10" brakes and changed the spindles too which I had, but the same could be achieved by using about a 3/16" plate behind the spindle. Without it the tire (or rim?) will rub a bit.

Reopening this old thread.
Problem - Jim Rea (bless his soul) set me up with original AMC dual booster and 1-1/8" bore master cylinder as I have put a Ford 8.8 disk rear in my 69 Javelin (he stated I needed the volume for the rear disks and also an adjustable pressure regulator). Sent everything off for rebuild as a unit and got back all the wrong parts.
Have ordered and installed a booster that fits but three attempts at finding and ordering that 1-1/8" master cylinder have failed. Jim stated it was an Ambassador MS but all have been 3.4 or larger bolt centers. The 69 booster is 3.2 bolt centers like a Ford.
Anyone have an idea of what master cylinder I should be looking for?

1. The wider brakes MAY move the wheels out some. The backing plate has some more recess to it in some cases, such as for the rear brakes, not positive on the front. The spindle may have a bit thicker base with the wider brakes to handle the offset of the backing plate, but I think no more than half the difference of the thicker brakes (brakes 1/2" wider, spindle base no more than 1/4" thicker... but I seem to recall it's more like 1/8" thicker). I put 64 Classic brakes on my 61 American, but that was back in 79 or 80! I don't remember any difference. They bolted up and I was running G78 tires (8" wide) with no problems.

2. Decreasing the bore increases pressure to the brakes, but reduces volume slightly. It does decrease needed leg force some. My advice is to try a 7/8", but check it thoroughly in a safe area before going out on the street. The pedal should go down a little further, but after the system is bled I think you'll be okay. Can't say for sure -- the wheel cylinder on the big cars are a bit bigger and need a little more fluid, but AMC used a 1" bore for small and big cars. You'll just have to try it, just do so safely.