The lnb would have to be manufactured for Dish Network, any other types will not work.
Not really.....
All DirecTV single and dual lnb's used in the Phase I dish are compatible with Dish Legacy lnb's and switches.
The best ones are made by Sharp. They made the original RCA, Panasonic, Toshiba and Sony lnb's, as well as a lot of Dish Legacy ones.
You can identify them by the Made in Japan label and the flange on the "F" connector socket fastened to the body of the lnb with two small Phillips screws.
I am currently using a 322 with two salvaged "Sharp" dual DirecTV lnb's. It is hooked up to a Dish500 bracket, two sw21's and a DirecTV Phase III dish pan (also, all salvaged).
One of the lnb's came from a DirecTV dish with a degraded cover exposed to the elements for about a year. The other came from an old Phase II dish that was over 5 years old. I have attached a picture of the first lnb, before removal and my current dish.
I replaced the broken cover on the "eye" with one from an old single lnb, also made by Sharp. The grey covers on both have been removed.
The dish has been in place for two years, now. It has been flawless.
DirecTV Phase I dual lnb's go for almost nothing on eBay and are many times thrown away in the trash.
All DishPro receiver's work with legacy lnb's. The heaftier power supplys with DishPro receivers last longer with legacy's. since legacy's do not draw as much power. Not drawing as much power, the lnb runs cooler.