I'm running the '91 Mustang GT seats in mine, but I definitely look out of the windshield closer to the top. It's not a deal-breaker, but it's as high as I'd want to go. I'd actually like to lower the floor in fact, but it hasn't been a priority yet.
Regarding the new holes in the seats, maybe Pops experience was the same, but there are already some dimples where you need to drill them to fit the factory Bronco sliders. Probably Ford has kept the same bolt patterns in vehicles for all these years, with slight variations. They were ready to drill and tap, and away you go.
I did end up moving mine rearward about 3" or so with new holes in the floor. Definitely needed it when compared to the relatively neutral seating position with the originals.
The big difference though, is that I can spend all day in these seats and still be happy I'm driving an EB!
The originals were only good for about 45 minutes for me. After that the rest of the trip was fidget-city looking for a good position.
Good luck in the hunt.
Paul