Well the engine is likely to be limited by the emissions and selling it as new issue. Sports cats and exhaust obligatory.
I cannot see (but would like to if they are going to use that title) a real power change which is the whole point for me. Given the current noise around Plus Six's that self park in an unplanned manner, if bolt a supercharger on these cars it could provide a spectacular moment given the V8 can make it lively already.
Add the suspension upgrade kit a few from the site have already proven is great for balancing the car out.
Lighten, Carbon wings and things?
Manual gearbox and lowered back axle ratio for a bit of in-gear zing.
Tillet seats and a roll hoop.
A bit of steampunk brass and slightly beyond distressed leather. Almost bare aluminium interior (might have a heat issue)
As mentioned by others, don't lower it unless you dry sump it!
Stack digital dash
Dual sidepipes