As much as I love spending other peoples money, Im going to suggest something a little older than most. Im a big fan of having something dedicated for spraying, it goes on the sprayer in the spring and is married to it until spraying is over, thats why I own an older SP, I knew that with cattle and hay plus row crops I was going to have to buy something to marry to a sprayer anyway, might as well have the SP with a hydro. 

I pulled a 500gal pull type my first year spraying and it was a pile of a sprayer, which was another reason for the SP, but I digress, I pulled it with an 8010 Allis powershift and thats what Im going to suggest. The 8010 would be too small for yours, especially in my hills, but something like an 8030 or 8050 with the powershift. They turn on a dime, have a nice cab, are pretty reliable and dirt simple with good adjustable closed center hydraulics, the transmission and hydraulics use separate reservoirs so if the seal goes bad on the pump, it can only contaminate part of the system. They can be had pretty cheap, you can get charcoal filters for the cab, and are old enough that just about anyone can repair one and you arent going to be held up by a sensor