Mike, sometimes the only modification needed is to turn the draft arm lift pins to the inside or outside depending on how the implement is configured. Also the eagle hitsh pins on Case equipment had a round head on the ends to keep the pin engaged inthe hitch, on conv. 3pt equipment it would be a lynch pin on the end of the hitch pin. I haven't seen too many 3 pt implements that wouldn'y directly hook up or maybe just a pin change.
I have a Danuser blade that I made hitch boxes for rather that just use a bolt and 2 nuts but that was just my wanting a stronger hitch point.