master cyl bore diameter ?

i found several sources that had a 70 rebel master cyl for sale thas were 1" bore.

All AMC/Ramblers (ever) used 1", 1-1/6", or 1-1/8" master cylinders. See this chart referenced here:

http://www.wps.com/AMC/Brakes/index.html

i compiled that data that i personally read in AMC Technical Service Manuals. Not Haynes or any aftermarket data. I could have made mistakes but it's from the horse's working end (you choose).

i'd find it hard to believe that switching from one extreme to the other would bother swept volume enough to matter, so switch bores as you see fit to fiddle stroke vs. pedal pressure.

for now i will be raising the hole about 3/4"(thanks for the idea)

try http://www.rockauto.com/catalog/x,carcode,1133110,parttype,1836

1979 Mustang, Manual disc brakes, 7/8" bore.

I have one on my 69 Rambler, it requires opening the holes up a bit in the firewall as the bolt spread is slightly different, but not to major. I also redrilled the Brake arm as the pushrod is shorter on the Mustang cylinder, check it against your existing cylinder before you return it, you may be able to use it. I changed the ratio on mine by welding the hole closed and redrilling close to the front of the pedal arm. A longer pushrod would be easier.

Anyway, I have a softer pedal with good action; however this is all on your shoulders as experimenting with brakes is, well, experimenting with brakes!

My Rambler has 82 Concord front discs and Factory 69 Rambler 9" rear drums.

I'm on my second 79 Mustang master, but have no real complaints and have not needed to add any valves or other gizmos to alter brake action. YMMV.

Also if your in a town like here we have 3 Advance Autos. When one won't help me match up something I just go to another. usually hit a helpful guy before going through all three. Then we have an Autozone and a Napa if all else fails. tell'em it's for a "streetrod" or custom build so they don't get all paranoid on you.