There were two snow plow frames commonly used on 8N's. One made by Dearborn and one by ARPS. The ARPS frame used two parallel pipes and the Dearborn frame was wider at the rear than in the front. Both used cables from the 3Pt. over some pulleys to lift the frame at the front. The ARPS was simpler, but the Dearborn was more common. I have an ARPS, if this is what you are looking at, I'd be happy to shoot you some photos.
In any case, make sure the front brackets are there with either make. And that the rear brackets are there with the Dearborn. They are hard to find. The rear brackets for the ARPS are easy to fabricate.
A photo of my APRS frame atached - mine has a Dearborn snow plow on it.
BTW, a Dearborn manual is available on-line at ntractorclub.com in the manuals section.
Contact me if you want more ARPS photos
kdmoser (insert at sign here) earthlink.net