Flying of grass won't be any big problem, I flew my T-33 as a D/F off our then grass field. We did roll it so it was smooth but the grass was kept about 2" plus high.
One great thing about the T-33 for grass field flying is the wheels are about 3" in dia.
I don't know about the p-60 combo, but any more power than that should give more than enough thrust for any good grass field.
The way the new gear are mounted to the airframe should yield great reliability on landings. I also found that the speed brakes worked very well at keeping the airspeed right on. It allows you to keep just a little power on and smooth out the approach.