Cheers Guys for your advices.
You are right Frank, that's what i want to do.
I start with the chassis because i think it's dangerous to bring a forty years old car on a track without any serious chassis check-up. I'll probably check simple things like gear shifter mechanism as well (coupler, bushing... because i know they can really make gear shifting better for cheap money).
For the engine, just a Dansk race exhaust and a K&N headers instead of this big black air filter box (could it decrease the perf?). I like a nice engine sound
I'm just worried about the front Boge suspension on the E (lack of torsion bar). Is it simple to replace by a normal bilstein setup (you need the full bilstein strut assembly?)