With Dodge you get higher rate front springs, larger diameter steering components, and a HD transfer case with PTO provisions. You also must include various option packages, so with Dodge if you get the snow plow package you also must get towing package (includes headlamp relay to take the load off the switch) spare tire and rear bumper (ballast) HD cooling (lower temp fan clutch, trans cooler, trans temp warning light and PS oil cooler) may be a few others too.
A plow prep package just makes sure the vehicle will support the rigors of plowing.A good plowing vehicle should have the strongest front end possible,HD cooling,trans and PS coolers,a HD trans and transfer case,and a large battery and alternator.If you have a vehicle already,it may have some of these,or you can add your own.
If your looking new,talk to a dealership who deals in trucks,not cars.We spec'd a few truck at the chrysler dealer next to us,who proceded to tell me,i need the trailer towing package,the heavy duty service package,and the snow plow prep package,to go with the diesel,and that i should upgrade to a HD transfer case,bigger 6500 lb leaf springs,and wanted add'l money for every little thing.Turns out,most of the packages overlap,and alot of the stuff came standard with the diesel.See if you can get a copy of the books they have to spec a truck with,and they have detailed breakdown's of what each package contains so you can pick what you need.If they want to sell you a truck,they will give you phototcopies.
On GM's the snow p[low prep also includes a relay to tkae the load off the turn signal switch(on C/K's).On 1500's /2500LD,it includes HD shocks,an engine oil cooler,and HD torsion bars.Newer models include larger radiator,and a 130 amp alternator.K3500 includes fuel tank and front differential shields.If your plowing,I recommend a test of your charging system,clean all battery terminals,an auxilary trans oil cooler if its an automatic.I also recommend at least a 3/4ton truck,it gives you a more solid truck with a payload cushion if you want to throw a tailgate spreader in later,or carry passengers,shovelers while plowing.get some good tires,and a cheap beacon or strobe at the least for 360 degree warning.