Around here, there's a ton of new truck dealers. They each have a bunch of trucks with plows on them already. I see an equal amount of Diamond, Western, and Meyer plows on them. Don't see any other brands at the dealers. My guess would be they will install any plow they can, as long as you buy the truck from them! Much like they will install any brand of dump body they can, as long as a customer buys a truck from them. The most popular brand of body I see here, is "Industrial Truck Bodies". They are in Elizabeth, NJ. Not sure if it's a national brand, or local. Industrial Truck Bodies also installs plows on new trucks too. Not sure if they do it for the dealers or not. They sell just about all the main brands of plows.
Looking over at Central Parts Warehouse, the Meyer Husky, and the Western Pro plow straight blade, aren't much different in price.
Meyer 7.5' (90") C 7.5 Husky - List for: $3,641.67 Sell: $2,485.00
Western 7.5' (90") Pro Series - List for: $3,672.00 Sell: $2,514.92
~Chuck