Get a raised winch plate. I bought a flat RC winch plate years ago, which worked fine with the stock bumper. But, when I bought a different bumper, the the front winch mounting bolt heads came in contact with the bumper, not allowing it to seat correctly. I ended up having to drill two large holes in my bumper for the bolt heads to fit down into. If it was not a cheap Smitty bumper, I might of had problems drilling through it.
Just a suggestion. I know Warns plate has a slight raise to it. There are others out there too.
Smitty winch, RC flat plate
Warn on same plate