That casting number is found on a master cylinder that looks pretty much the same as the '71-75 disc brake master cylinder used on most Chrysler products. That master cylinder uses the casting with number 3461187. I've had those two master cylinders side by side and the only external difference I see is that the outlet bosses on the one you have don't stick out quite as far.
I haven't taken them apart to compare the pistons. However, I assume yours would also have a 1-1/32" bore, and the kit for the '71-75 disc brake Mopars would most likely be the one you need to rebuild yours.