Edited to correct content ...
I haven't mentioned much about the '73 engine yet, but it really is time to let others learn from my mistakes. When buying a used Fiat, I recommend looking for an "honest" car. On an "honest" car, there will be ample signs of aging or properly accomplished repairs, the car will be mostly assembled with only a few parts thrown in (perhaps the original breather if a chrome one has been installed or an extra timing belt) and finally, the parts that are on the car will make sense. This car only passed one of the three tests. There were parts everywhere, the front bow, carburetor fan and breather were not installed and the carburetor had a vacuum secondary. Just in case you are new to Weber carbs, the two pictures below (gratefully borrowed) show the ADFA with a mechanical secondary (top) and a DHSA with a vacuum secondary (bottom).

In my '78 I should have expected to see the top carburetor, but instead I saw the bottom one. Note the big difference as the bottom carburetor has the large round growth in the upper right corner. Before purchasing the car, I Referenced the great carburetor guide from Mirafiori.com (
http://www.mirafiori.com/~corey/How-To/Carb.htm), and noticed that it was likely that this car had a DHSA carb. The DHSA carburetor is generally not as desirable as the ADFA that the car originally shipped with (vacuum lag when engaging the secondary and a smaller primary). The thing is that I knew it looked wrong when I saw the carb the first time and I knew that it was likely that it was not an ADFA carburetor, and yet I didn't dig deeper. From this I have developed personal rule #1 ...
Personal rule #1: People that know what they are doing on a car and are not flat broke tend to replace parts with ones that meet or exceed the original specifications. If the parts don't meet or exceed the original specifications, the last guy was too short on cash, brains or time to do the job right.
So what do you get when you have a pre '74 carburetor on an engine installed in a 1978 vehicle ... in this case you get a 1972 engine. Funny thing about 1972 as opposed to 1978 ... they didn't use as much unleaded gas back then. The gas tank fill tube is wide open like you would expect from a car burning regular gas (have to accept the fact that the gas tank was probably "borrowed" from a different car (possibly the '72 or '73). Despite the evidence for the engine originally using regular gasoline, there are catalytic converters in the exhaust.
It gets stranger, there appear to be two of them. The first is an old OEM style near the headers and the second is a modern converter just before the muffler. So I have a 1972 engine that wasn't really designed to run unleaded (the lead acted as a lubricant and sealant around the rings) with a tank that is set to accept regular gasoline, an exhaust with
two catalytic converters a catalytic converter and a 1973 carburetor. There are reasons that I call this car a FrankenFiat.
The moral of this story ... if one thing doesn't look right, take the hint. There will likely be a lot more to find just beneath the surface. Oh, the answer is yes, I would have still bought the car. I just might have haggled the price a little better.