Sorry, but need to know more info. If you want, I can set you up with a 12' disk that needs a D8 to pull them. As far as what I would call a normal disk, my 12k pound 75hp tractor will only pull our 12'JD disk on basically flat ground. But there are other disks out there that you should be able to pull. Do you have an idea of what the 12' disk that you want to pull weighs? What size disks pans? What type of ground? Flat or hilly?
Our disks have 22" pans that are 3/16" thick, weigh in the 4000lb range I believe, is yours similar to this? Most of our ground is hilly, I usually just pull our 8' JD offset disk and don't have any problems.
JD 4520, Toolcat 5610, Bobcat S300, Case-IH 125 Pro, Case-IH 245, IH 1086, IH 806
In general, the "typical" pull type, 12' JD disc used for farming will be fine. In general, I refer to ones which have 4 gangs of angled discs with 2 lift wheels and single cylinder to lift the disc. You should have the hp for most conditions and certainly the traction to do it.
The disc is an older JD BWA. It has 20 inch discs spaced at 9 inches. I do not know the weight. It is not an offset disc. I will be using it on hilly ground with sandy loam soil.