For 'road' use, may I suggest that only "Grp 2" wheel-arches are used---Grp5 ones are really too wide. "Nanni Ricambi" also sell these wheel-arch extensions, but are notoriously difficult to deal with if you live outside Italy. (any mates or relatives in Italy?). When you are fitting the extensions, the wheel-arches of the original wings need to be cut back, and then the inner and outer wheel-arches have to be welded together, to prevent any 'flapping'. I used 'riv-nuts' (5mm) to secure the extensions to the wing outers, 5 per extension. If you want some pictures of my wheel-arches (without the extensions fitted), e-mail me direct, and I will put some through to you. Whichever you buy, be prepared to do some fettling!!