There is a lad who fitted one in a megane coupe and has used a combination of standard renault mounts for the top mount and gearbox mount.
There is also another lad who has a mk1 clio valver and hes fitted the crank, rods, pistons from a f4rt engine into a stock f4r bottom end. He's then fitted the f4rt cylinderhead along with the turbo manifold an inlet manifold. By using a f4r bottom end he's been able to stick with a jc5 box and the last time I spoke to him he was blown away at how much better it was than his last engine, a fully forged high comp engine running itb's.
It's easy to say "i'll just drop this 225 lump and gearbox in there" however there's plenty more headaches than just getting the gearbox to fit.
* megs run cable operated gear linkages
* megs have hydraulic clutches
* You will need custom driveshafts, how will you achieve this when it's undriveable in your garage?
* the meg and clio ecu's are different, so which one will you use for full engine control?
and there are many more complications.
In theory its a great idea, however unless you have plenty of cash and alot of engineering knowledge it's likely to turn into a nighmare.