I think you will be fine with the 231 then. It came behind the dodge trucks with the 360s so it should hold up fine for what you want to do with it. Although I do have a failed np231 in my garage right now that came out of a 360 dodge 1500, but I think high mileage and lack of maintenance are the reason it failed, It has over 225,000 on it and I don't think the fluid was ever changed/checked and it had a leak.

 

00T, I agree with all you said!