To be more specific -- the 15% engine set-back and the 3" hood extension limit -- in combination -- limit the wheelbase. You can't move the front axle far out front without violating one of these. And you can't move the engine back (for the same reasons) without encroaching on the driver's compartment (which you can't extend). And, of course, you can't modify the bodywork from the cowl back at all, so you can't extend the wheels out the back.
All in all, these restrictions have kept most of the Street Roadsters looking like street roadsters.
Some have removed door hinges (which I would define as streamlining) and punched holes in the radiator shell for intakes (which I believe to be at the very least re-contouring {not allowed}, and decreasing the overall surface of the grille shell below the minimum, also not allowed).
Stan Back