Good call Rene, if it's not for you it's not for you.
I had similar reservations about the modern donor route for the SWB - if you look back through Geoff's thread you'll find me asking if the MGB GT could donate its mechanicals - but I've come to terms with the Z3 as a suitable starting point due to the difficulties of cutting the shell on the MG.
I'm aiming to lose a lot of the modern feel when I build mine: the interior will be totally late '50's, while I'm leaning towards original sized, 185/80/15 tyres too (excuse the pun), which should soften the ride and give a more authentic feel to the handling.
Best of luck with whatever project you choose next, keep us posted.
