Hydro Ax 411EX

I'm considering buying a 1998 Hydro Ax 411EX that was used as a feller/buncher. It comes without the head and I would buy a used 8' rotary ax mower that came with the older model Hydro Ax.I have a couple of hundred acres of heavy brush to mow that is 10' to 15' tall with a base of 2" to 4". The machine has around 150hp and I'm concerned it may not have enough power. Also, how do I determine if the pumps have enough flow and cooling capacity to continuously run the mower under heavy load?
Hope someone out there has worked on a similar conversion. Thanks.

Hydro Ax 411EX