Clearly there is a lack of knowledge on how long diesel motors will go for. 300,000 is not very long for a good diesel to last.

I agree that if we are talking gas only the Toyota will last longer than most fords,chevs,and all dodge gas trucks. I think the main problem with towing with a gas truck is going to be the valve body in the trans cracking from too much strain and multiple other trans issues. Manual Trans is the only way to go if your gonna "tow" with gas.