Fecon or Denis Cimaf with a DCR rotor are the best brands IMO but it all depends on your budget. Those will easily run over $30,000 so it really depends on how much your willing to spend on a head.
As far as the skid steer your wanting to use I’m not familiar with that model but as long as you have a poly windshield and an enclosed cab you can make it work but you will have to have those 2 things at the very least, you can also buy a low flow head if your steer isn’t a high flow model as well they just don’t work nearly as good.
50 acres on a steer is going to take a long time to accomplish but again it’s doable if you have the time to do it. I would venture to say the steer might be worn out by the time you get finished though lol. Mulching will find every weak link on the machine and it’s super hard on them.
If your simply cleaning up underbrush and not cutting trees you could get by with a brush cutter with mulching teeth on the bottom for a lot less money, I’d recommend a Vail X Series brush cutter if you go that route for about $13,000. I have a couple of those and their built like a tank and will take the abuse and work exceptionally well not to mention their customer support is in a league of its own.. Shoot me a pm if you have any questions and I’ll be glad to help you out, I’ve had and ran pretty much everything made at one time or another. You can’t skimp out on a cheapo unit whatever you do or you will be working on it more than your working it.