FWIW, I have a Nuovo Record RD on my MK IV. It is a rider, not a show piece so right off I ditched the original Campy jockey wheels - almost no teeth and cracked anyway. I installed contemporary plastic wheels. I also ditched the old school chain and FW. Now has Suntour Ultra 6 spd 14-28 and a 9 spd chain. R wheel about in the middle of the DO slot. As reliable and quiet as a sunrise. Just snicks from gear to gear, up and down, with rarely any trim needed.
In in the past 6 years, no one has crouched down to inspect my drive train and berate me for non spec parts. I just enjoy the ride, often.