I'm about the same size as you, and it's going to be a very tight fit. Especially with a helmet and 2" of required clearance. How you set up your seat will be very important, and you might find yourself needing to look at a formula car style seat to meet the safety requirements.
If your sanctioning body will let you drop the floor or perform other major body and/or chassis surgery then you have more options. One avenue I considered (when I was planning to cut mine up into a race car) was to replace the firewall, part of the floor and and create built-in side bolsters and then use a pour-in seat with a six point harness (like a formula car or sports racer). I did have to request specific permission and pre-approval from my sanctioning body in question, but they granted me a go-ahead subject inspection and final approval.
That said, if you end up deciding not to build a race car out of your shell, please drop me an email. I'd still like to build a racing Europa, but I've just decided mine is just a bit too nice to butcher. It's a complete, running S2 with only 23k mikes, but needing a full going over from age, garage malaise and dis-use.
