Have just had my MK3 30,000 genuine miles! Converted into S2 RsT. Was a nightmare the following were changed for the conversion:- Bonnet, wings, front panel, scuttle, tailgate, rear panel cos lights sit different, front suspension inc anti-roll bar, doors (cos the trim fixings inside are different) even the bulk head is bloody different where the steering column mounts up. Also in my conversion the engine mount on the inner wing required changing cos the engine sits low in a MK3!
Ur conversion shouldnt be too bad if ur just going for external looks only.
Was it worth it? In this case it is a mint car even the underneath was taken back to shiny metal and acid etched etc. May add a couple of photos when i work out how to do it.