Need help to identify differential

[Peanutbutter]

Hi guys, I don't seen to be able to spend much time here latetly but maybe things will get better. I finally got started work on my 1966 C80 series napco, got it down to bare frame to start sandblasting. I'm more concerned about the front axle, in dire need of new ring and pinion but having trouble identifying. Its a rather large square tube housing with napco tag riveted to the front but it looks like they used 1960s eaton carrier in napco housing. I understand eaton had five differentials starting with the HO52, then HO72, then an 11000 lb, 15000, and last is 17000lb. My ratio is 7.20 with 5 and 36 teeth and I thought it might be the 17 but when I checked the only single speed I had discovered it was to big. Now I'm thinking it must be the 1100 or 15000. My big single I checked tonight is oblong and bolts up with 13 bolts, the one I need is completely round and bolts to housing with 10 bolts. Need info to tell difference between the 11, 15, and 17000lb. Will post some pics tomorrow night, maybe they will help. thanks, Wes