As the title says, the brake master cylinder for a 50's-60's Jeep CJ is almost identical to the 580c master cylinder. The mounting holes appear to be exactly the same. Dimensions are almost the same. The only 2 major things that I noticed is that the fitting size for the brake line is different. Also, the size of the pushrod might need to be adjusted. Seems like there aren't too many options for 580c master cylinders. Either you buy the cheap Chinese ones or spend a mortgage payment at the Case dealer. You can get a much better quality CJ master cylinder. And they're usually cheaper.
Oh, and the neck where the brake line connects is longer... But it's not like there's a clearance issue on the 580
Just eyeballing looks like the mounting holes on the lighter colored one are further apart.
Looks like that in the photo but I measured them and they appear to be exactly the same
If you can overcome everything else, the only other issue would be the bore diameter of the master cylinder. The brakes are just like hydraulics, there is a ratio of the master cylinder bore to the wheel cylinder bore. If your purposed master cylinder has a little bit smaller bore, you will find while you have good braking power, the pedal travel may be excessive. If your new master cylinder bore is larger than it should be, you will have a nice high pedal, but it will require more pedal pressure to achieve the same amount of braking pressure.
It does look that way to me as well.
Probably the angle of how I took the photo. I measured and also got 2 long bolts and ran them through the mounting holes and they appear to be identical.
As mentioned above, bore and stroke of the master cylinder are the most critical. Anything else can be adapted, but if the volume/pressure aren't right you're fighting an uphill battle to make it work.
Appreciate the replies. I figured it was at least worth a look given the spotty quality of these aftermarket units