If you just want the wide rear arches, but want something a little plainer, just get Maxi arches. Either way I think you could bodge it and bond the new arches over the top but the proper way is to cut away the originals. Im no expert on that though. It would definitely look weird with a normal width front and rear bumper. Perhaps if you dont like the Alien bumper and youre prepared for a bit of bodywork you should think about budgeting for the cost of a cut n shut job on them (and the respray) to pull the bumpers out by a couple of inches to match up with the new arches. Or look at a complete Maxi kit which is IMHO the best kit you can possibly get for the mk1 Clio...the fact that you dont like the Alien front bumper, dont want the spoiler and rear bumper and only like the arches, means you basically dont really like the Alien kit! Maxi kit is basically Clio 16v/Williams factory style but 100 times tougher and wider looking. As youd expect of a copy of a factory Renault rallying kit.