Shell Rotella 15w40. My old man has been wrenching on trucks and tractors since, before I was a twinkle in his eye. Everything we ever rebuilt, whether it was a Perkins, Cat, Waukesha, to a 1.6 Escort motor, got Rotella in it. It has more ZDDP in it that the off the shelf automotive oil. So, the 261 will apprecitate that. It may be a little thick for those zero degree temps, but if you're working the old girl it's the right way to go.
For the rearend, any 80w90 hypoid gear oil will do.
For the trans. Some say 50wt Non-detergent motor oil. Other's will tell you 80w90 gear oil. I can't say either way.
