Wheels
Virtually all Fiat models have the same PCD for their wheels, at 4 x 98 (four stud/bolt, with 98mm between opposite holes).
They also (mostly again) have the same bore, at 58.1mm
So the only variables you need to look out for are the rim width, and the offset (between the mounting face and the centre-line of the wheel's rim width).
There are many lists on the net, but some of them seem to contradict each other regarding the offset, or they give a 'range', e.g. 35-45.
http://www.mankymonkeymotors.co.uk/Tech/pcd/pcd.htm
http://www.carlsalter.com/fiat-wheel-fitments.html
This explains all the variables...
http://reviews.ebay.co.uk/Alloy-wheels-amp-P-C-D-comparison-by-KERBSIDEMOTORS?ugid=10000000001037254
What that guide doesn't mention, is probably the most important factor.
The bore in the wheel should fit tightly on the boss of the hub, so the weight of the vehicle is carried by the hub, not the wheel bolts/studs.
Most modern cars are designed to be 'Hub Centric', where the hub centres, and supports the wheel (and thus the weight on it).
Older cars may be 'Lug Centric' (US terminology I think), where the weight is carried wholly by the wheel studs/bolts, i.e. the bore
doesn't sit on a matching diameter boss on the hub.
You can get adaptor rings for when your wheel's bore doesn't match the hub boss, but that obviously only applies when the bore is larger than the boss.