im not a purist in any way so don't be offended please

i fancy a mk4 escort convertible rs turbo
I'm aware that none where actually made by ford

so whats easier
buy one done or buy a normal one and do it my self
i will do a full rest and bare metal respray so ill have to totally strip the car and also re build the engine
but my questions are
how easy would it be to find all the parts needed to convert and what are the costs likely to be
what other turbo'd engines are a option
has anyone here done a build on the forum
thanks