The leaning might be related to either some damage to the underbody or missing spring rubber(s).
The "penny washer" shims are intended to be trial fitted whilst the suspension arms are in a Fiat jig assembly. It locks them in position at which stage you can work out the correct number and sizes of shims fit at each location and at what sides of the bush they should be placed.
Without that jig, (hands up who has one) you can only go by where they came out from. Even then, if you replace bushes the process needs repeating.
I tried not to lose sleep about it on my car because I could see no economical solution to it.