noo not far fetched at all , in fact its been done lots of times ......
the only reason i say you me need the quarters is that im not a 100% sure if the profile of 3dr quarters is the same as the base model , or if it was slightly different , ( sure someone will clear that up like ) but i suspect finding good condition rear seals will be the hardest task , from what jacko said b4 they have locating tabs in them wich tend to break with heavy handed removal ,
seems like an easy way to get what you want mate , although its never going to be a cossie on the book , done right im sure it will pass to 99% or the joe public ,
good look with it mate , get a resto post going ,
beef