I'm with Johnny on the SG for temp monitoring and grill blocking as a reasonable place to start. The SG is a great investment anyways and the grill blocks can be provisional at first to see if they're worth doing for MPG (and it's probably the easiest/most immediate spot to clean up aero). Cardboard, plastic, tape... whatever is lying around. At this point looks aren't a priority so much as performance to me (says the blue tape guy
).
As for wheel covers you can even use venerable tape again just for testing although you do have more gaps so would require a bit more tape coverage.