First thing I want to change on my 997.2 is the standard PDK steering wheel to the Sports Design wheel. Does anyone know if the 991 wheel will fit as there seems to be more of these avail on the secondhand market?

 

991.1 wheel should be a direct fit.
991.2 needs an extra adapter i believe and new airbag.

 

I think that's right. I believe the 991.1 sport design wheel is the same as the 997.2 sport design wheel.