The later knuckles are a lighter weight one piece casting, and do not have the removable caliper mount, and the brake pads are of a slightly different size. The later pads are slightly longer, but thinner, compared to the early pads (IIRC). The surface area of the two pads look to be near identical, the piston area looks identical as well (I have not gaged either piston so a small difference may exist).
FWIW, I have both sets of knuckles and decided to stay with the early knuckles, and hub/rotor/pad set-up on my 88, because they look stronger when compared (side by side). I was ready to trade to the later knuckles as well, after blowing an early knuckle apart, but the information regarding the possibility of a significantly larger later-model brake system proved invalid.
There looks to be no brake area advantage to either pad configuration, only a cost advantage to manufacturing the later DC design (compared to the early two-piece K-H design).
The early Kelsey-Hayes knuckle has/had the advantage of larger aftermarket bolt-on caliper mounts, and calipers. I do not know if these parts are still available (or an advantage over the more recent WJ knuckle and brake upgrade).
If anyone wants to trade up to the later knuckles, or has early spares thay cannot use, I am willing to trade the 97 knuckles I have for early knuckles (for my trail spares cache).
