Hello, i saw your post. If you cant find any stock stuff to bolt on you might think about a wilwood setup.
If you buy the kit on Ebay it will run you about $700 or so for the conversion kit. You'd need another master cylinder to match probably another 100 or so. and then unfortunately there is the fact that no one makes a kit to fit 4 lug rotors, let alone 13" wheels. SOoo you'd need another few hundred for some 5 lug wheels which you would most likely want to find as a set of 4. And then you'd need to do something about the rear lugs. The axles could be re-drilled , SIGH!
SO yes that way gets very expensive very fast.
HOWEVER all that being said, the braking performance and stability your daughter will get out of the car will be priceless.
My 71 has manual Stock disk brakes and they require a hard push to stop. IT stops very well for 9in rotors. Its just that it doesn't bother me being a guy. So a firm modulated pedal is no biggy for me.
Sorry to rave on, just that Ive been and am in the stock brake route, and if i totalled up what Ive spent on my brakes in all new parts, just to have factory stopping, id be sick. Ive probably got 300 in them. Rotors, calipers, lines, etc etc. Not to mention that to replace my wheels with 5 lugs would be up there.
SO if you do go stock, look hard for nos rotors on ebay if your very lucky, as replacements are available but they are ridiculously priced. 145 at oreillys auto. They are 2 year only rotors. And no, 74 stock type stuff just doesn't bolt on at all.
I hope ive been help full if not informative.
Good luck!
Robert