On GM trucks with plow prep package, they have increased front end capacity, larger output alternator, auxiliary light switch with wiring harness above headliner for roof lights, large hole predrilled on firewall for routing control harness under the dash, transmission cooler, etc. I am sure I forgot something else, but you get the idea.
Ask your dealer or the plow dealer what the code would be on your door sticker or VIN to indicate that your truck has the plow prep package. On fords, if the front GVW is over 4900lbs (I think, but should be close if I'm wrong) the truck has the plow prep package. For F150's and F250's if the total GVW is over 8600lbs then it has the plow package. But the key is the front GVW, because the tow package only beefs up the rear.
My truck (F350) did not have the prep package. I had to add a leaf to the front to handle the weight of the plow. Never had a problem with the altenator, may even be a high output for the tow package, not sure.
If you have a V8,then I'd recommend a 046/047 spring combo.If it's a diesel or V10,then use a 047/048.The lighter spring (smaller number) goes in the pass side.You can get the springs from your local Dodge dealer.
They are pretty stiff springs,but they hold the plow real well,and don't affect the ride to much.Handling is much improved too.
Those prices are in US.You may be able to do better if you shop around.
The springs aren't hard,just drop the shocks,and the sway bar links,and down comes the diff.You may have to pry down on each side of the diff to get them out,but they will come out without a compressor.It should take a couple of hours for a novice to do them.