I actually ended up going to NAPA last night, and with the help of an awesome gal I found a car oil drain bolt that fit PERFECTLY. I didn't have to shim it, trim it or anything. It measured 0.42" long from the base of the head, which I thought was too short, but it made the drum valves line up perfectly with the edge of the main exhaust port. Anyone else needing one should check into Auto oil drain bolts. I'll try to get the part number next time I'm in NAPA.