I’m assuming given you’ve mentioned a GT3 that you have a substantial budget in which case I’d be looking at
@Gibbo ’s M3 thread I wouldn’t go for a CSL - they are expensive and you’d arguably kill much of its value by modifying it too much - but a regular e46 with money thrown at it would be my thought process especially having followed Gibbo’s exploits and given his praise of the e46 not to mention the type of cars he’s ran and tracked.
Out of the box would I’d guess mean a GT3 but I’m sure you’d soon be adding to it which almost negates the out of the box requirement if you see what I mean!
Why change the Mini out of interest? I ask because my boss is a track nut and full on petrol head (daily driver of a 458) but he’s got a track prepared Mini (built by Lohen
https://www.lohen.co.uk/ ) which he trailers to circuits and when I asked him if he ever tracked the Ferrari his response was no because the Mini was better!
I suppose it boils down to requirements, if it needs the compromise of being a road car as well as a track toy then I guess your options are limited, what’s the deal with regard to that aspect?