just to make you aware of the costs involved though, i hope you're aware that the engine and gearbox + auxilliaries alone are going to run you into the best part of 3 grand and tailor another 1.5-2 grand into the total cost for the labour involved.
however, i'd have to say it would be worth it because a twingo with a megane lump (280bhp easily after a remap alone) will be something to treasure for the rest of your life, no cars on the road could match that level of performance. tailor the ridiculous engine, power to weight ratio, LSD...all in with the best chassis on the road by far.... hmmmm i'd safely say that would get me as excited as any expensive super car ever could!