Oil pan nuts, which ones go where?

Sounds like you have "bolts", technically termed "machine screws", not "nuts". I forgot, but the special ones are likely around the front and rear crankshaft exits. Be real careful torquing the rear ones since those go into aluminum holes which are easy to strip. Indeed, I would test-fit each bolt first to insure the hole is good and they don't "bottom out". Blow out all the holes w/ air. There is a good writeup by Dutra on www.slantsix.org on installing the rear seal and pan. Someone linked to it just yesterday in a seal question.