First, I believe that the steering gear uses an open center valve. I think that this means the winch would have to be in line, not in parallel, and an open center/power beyond valve would have to be used. Pressure line from the pump to the winch valve, pressure line from the winch valve to the steering gear, and a return line from the steering gear to the resivoir.
You'd also want a pretty significantly sized fluid resivoir, otherwise I'd expect the fluid to get old pretty quickly. Winching (or any extended use application) is hard on hydraulic fluid if the system errs towards the small side.
The above concerns about the pump volume are probably accurate. There's also the issue of how much horsepower the front cover really "want's" to deliver. A larger pump may fit, but that may or may not lead to further issues. I'm not sure how you'd research that?
I would think in the end a PTO pump would be a more prudent solution.
.02 only..... I'm not an expert here, and of course I'll always (within reason) go along with the "bird in the hand" theory.