Hi EMU,
The soft I use has a feature called "multi section surface generator" where you specify a curve profile, then place several sections along the profile and let it generate the necessary NURBS in between. See sketch below of what it would do here.
I would handle the wheel covers separately. In fact I would design half and do a XZ plane simmetry afterwards.
If you tell me the rough dimensions you have in mind, I can look into it one of those evenings.

edit : it might make it easier to print the 2 halves separately.

EMU.jpg