Sorry, I'm an AC man through and through...but good luck with those engines if they're putting out the power you say. They will scatter someday
Why do I think it's too much rubber? Because I do this for a living, and I know how much weight it takes to run certain sizes of tires, and at what power level they're needed at. Bigger is not always better, a proper match of power, tire, weight, and application is what makes or breaks a tractors performance....FACT!!
Now, will they work, probably do...do you need that much tire, nope...not enough power!
As for the power shift, I'm sure it works OK, but a 12 speed power shift has lots of gaps in speed ranges, that a 20 speed Power Director doesn't. As long as you can find the gear you want, wonderful, I'm happy!
Oh, and IMHO, any dyno that is "maxed out at 225" probably is older than the tractor, and could use a calibration. My dyno will handle 475hp (depending on RPM, of course). Again, not trying to be a dick, by PTO dyno's need calibrated fairly often, and the numbers are only as good as the operator is honest. I can show you whatever power you want to see on a PTO Dyno, or I can be honest and measure torque and figure it from that...that needle doesn't mean squat if she's not set right!
Chris