I have a 90 Dakota 4x4 318 with a 7'6" 25 series Snoway with the down pressure system(dps), i got the plow with the truck when i bought it used , Down pressure is a option I would spend the extra money to get it. You need it if you get the lexan moldboard it helps alot with backdragging. As for the truck i have modified mine slightly, Trac Loc lockers and 3.55 gears front and rear, that helped alot in the tracton department, pray for snow!!!
Downpressure is definately worth the cost. Not sure how much it even adds as I've nver tried to get one without it. We're running 3 Sno-Ways if that adds any credence to my opinions. Only problems we've had has been with some poor welding, it pays to looke them over VERY closely about twice a season. We've had storms where it was sort of a mix of rain/snow/sleet, maybe 1 1/2" thick, we were able to cut to pavement, guy plowing the next lot over with a Fisher was only able to cut the top a little.