I agree with Erik on this. Doesn't make much sense to source a knuckle and modify ball joints when you can easily fabricate, or have somebody else fabricate, an adapter bracket for any caliper. Dealing with possibly multiple difference in knuckles (strut to knuckle alignment, tie rod fitment, ball joint fitment, axle shaft spline count, etc) just to make a caliper bolt on? Lots of people on this board are using 3000GT, Camaro, Corvette, and other calipers with custom brackets and I don't think anybody has had trouble with them. IIRC, Wilwood makes an adapter to mount their calipers on our cars. The car I'm building used to have Porsche 996 front calipers with a custom made bracket. Now those are some calipers! (Too bad I couldn't afford what the seller was asking for them.) You can put together a killer brake system without spending a ton, or having to modify things much at all. Look up the how to post Curtis made about using an Infinity master cylinder as an example.
*EDIT: I see now that brackets have been discussed in this thread, I think I confused this thread with another one somewhere...anyway...I vote for brackets over swapping knuckles.*