The parts I used were at the upper level of what would work, so I could have done it cheaper. The pump was $250 and 6 gpm. The boom less nozzle was about $100, tote was $50, and plumbing was probably $100. On another thread I started, "sprayer decision, please give me your opinion", I showed pictures and discussed ideas. Sorry I don't know how to link this. I can email pix if you like or put them on this thread tomorrow. I also have a 25 gal Fimco ATV sprayer with a boom from Tractor Supply. My home made one is much faster, only less maneuverable, since its in my longbed cab F 350. I made the boom less jet frame to fit in a receiver hitch, so any truck would work. For my initial trial run, I sat in the bed while a buddy drove, and I operated the switch. But Fimco makes a cheap keychain remote that would allow operation from the drivers seat. I may eventually add a 12v remote operated valve. I spray all my plots and roads, probably 10 or 15 acres with 250 gal in my tank. Drove a slow consistent speed. Worked great, got very even coverage, and killed everything. I planted last weekend and nothing green was seen.
I also debated about making it 3 pt hitch platform, but I like doing it from the comfort and convenience of my truck. Another nice sprayer you may want to check out is one made by "briar hill Brittany's), who detailed one he built, using a roller pump.
Building one is fairly easy. Of course you could get more complicated with foam markers, but I had no problem using my tire tracks as a guide. Probably overlapped some but that was no problem. I especially like being able tp put down 275 gal quickly without refilling.
For an open pasture, I think mine would work great and I think your pump would be big enough to drive it. I see some of the boom less jets on eBay cheaper than I paid retail. My jet probably sprayer 50 feet originally which was too wide for my narrow plots, so I plugged 2 of the 5 jets to cut it down to 30'. The spray pattern I showed on my thread was the cut down version, not the widest. For you, I would leave all jets open and let her rip. Just drive around and dump 250 gallons quickly.
By the way, I could convert mine to a boom in less than a minute as I designed it, but see no reason to ever do that.