On large trucks we suggest they mount a seperate filter in the return line... . usually a large oil or hydralic filter... . we've used a 2 qt filter ourselves on our larger trucks... .
This not only filters the oil, or power steering fluid, (some truck power steering gear boxes use engine oil) but it adds 2 qts to the system and allows it to cool down more... . I'm guessing if I had a plow on any of my trucks, that's what I'd do.....
I currently own (3) 3500's and 2 of them have over 220K miles now..... with no problems... . Hope this helps.....