This topic goes round and round on loads of Forums. I think the "best" car depends on your purchase budget, how much you're willing to spend over time modifying it, and how much value you expect it to retain at the end of the process
In general, the more you modify the car the worse it becomes on the road and the lower its value drops. So I'd reckon on getting nothing back for the mods and on the overall value dropping
The main things I've learnt from doing track days are:
* if you're doing it seriously you'll need a set of track day wheels & tyres. If your car isn't big enough to carry them and a trolley jack you'll need a support car
* it's hard work driving the track day car home after a long day and having just swopped back to the road wheels & tyres
* breaking the car and going home on an RAC Recovery wagon gets old very quickly
* the more you modify, the worse the car is on the road and the more your costs go up
* Insurance companies do not like roll cages
My advice would be to have a "Track Slag" and to tow it to events behind your day-to-day car. That way you can drive up, roll the track car off the trailer and it's immediately ready to join the queue. Tyres at the right pressure, fuel in the tank, windscreen clean, belts adjusted, wheel nuts tight & etc
I can't comment on the 350Z but heavy cars are always going to work brakes and tyres harder than lighter cars. Older cheaper cars like BMW E30s have lots to recommend them, and are great as learning tools, but they're obviously wrong if your main motive is pitlane one-upmanship rather than driving. But I wouldn't underestimate the bragging rights of a well-sorted E30 M3 - it'd be half the price of a 350Z and it wouldn't depreciate like falling girders
Nick Froome
www.w124.co.uk