`NB or NC for Fi?

OK, so I love my V Spec, and have no plans to change it, and will (I hope) keep if for ever and a day.  Well, at least until the demon tin worm eats it.

So....

Now and again, I feel the need for speed.

Lets be clear, I have owned fast cars, including Porsche, fast motorbikes and even a slow plane. But I love the whole thing about MX5's added to which I love to tinker.  I had been toying with the thought of an R53 Mini Cooper S, but keep coming back to the MX5, and a project is something every boy and girl needs. So now the V Spec is sorted, it is time for some extra whoof to the Zoom Zoom.  Where to start though?  I cant decide between an NB or NC to convert to turbo (I dont want to do an NA for my own reasons):

NB

• Cheap
• Loads around, but loads of rust buckets too
• I know my way around the NB (well, its an NA really)
• Better stiffening than an NA
• Front frame rails (gulp!)
  
• Well known road to turbo