The plethora of absolute guesses and wrongness in this thread is amazing.
It's indeed a Fiat 850 Spider, a 1973 model by the bumpers, which is the last year before it was replaced by the X1/9. The wheels are nothing special, they are just factory alloys off a X1/9 most likely. It's rear engined, not mid. They did bring rusting out to a new level, thanks to a British quality top fitment and rubber floor coverings that trapped water underneath for starters. Check carefully the floors, X member, rockers, trunk floor (particularly under the spare) and most important the front suspension mounting points. If it's solid in these areas, it's very much worth doinking around with. This year came with the largest engine offered, the 903cc. They don't accelerate very quickly, but will do highway speeds with no effort. Very few exist because they were disposable, did rust pretty easily, and Fiat did indeed buy thousands of them back (I have the recall packet from my local dealer). I really liked mine, but it was as (un)reliable as a LBC and nothing like my 124 Spiders.