It should screw on without any problem, the MGW shifter uses the same thread size and pitch as the stock shifter. I have used a factory shift knob on my MGW with no problems.
I just bought a white hurst ball with the letters HURST engraved in the side of it for a 05-09 GT.
I have an 01 Cobra and they don't make a white ball with the HURST engraved on the side........so I drilled it out and tapped in some new threads in and it works like a damm on my MGW!!!