To clarify the front brakes thing.....

306 gti-6 brakes DO fit straight under standard 15" wheels, as does the other popular conversion which is 307 hdi (same as 206 gti-180) front brakes.

They both use 283mm discs, however the gti-6 discs are 22mm thick whereas the 307/206 discs are 26mm.

The difference between the 2 calipers is that the gti-6 caliper has a 57mm piston and the 307/206 caliper a 54mm piston, and a standard 1.9 caliper is 48mm.

I chose to fit the 307/206 calipers for a couple of reasons - they are pretty cheap new, but also, they dont affect the feel of the pedal toooo much! When fitting the gti-6 brakes, you really should be thinking about changing to a larger master cylinder from specific 405 models as the pedal travel becomes a lot longer.... With the 307/206 brakes the pedal becomes slightly longer but still feels good to use and so doesnt require a master cylinder change!

Regarding engines, IMO if you find a decent car with the engine installed well and its been well looked after, then an Mi16 powered car is the way to go! They fast and fun, and pretty cheap to maintain. The 306gti-6 engine would be the one to have but i dont believe its anything like as easy to fit as the Mi engine!

Good choice of car Spiky