Since you're in the US, you're probably in a fairly good position for finding Ferraris of any sort, shape and condition. In regard to importing one, you would probably spend enough on transport, duties, taxes and compliancing to be able to pay for a car in good condition sourced locally, so importing is not an economically great idea in my opinion.
You may wish to consider a relatively high-mileage example in reasonable condition. Your chances of finding a 308 matching that description is better than finding a 328, but the basic principle remains that the car may need some major mechanical work done on it soon, but it won't require total restoration. At
http://cars.desertworld.com/ma75gt4.html is a 75,000 mile 308 at around $18,000 - 19,000.
As to more specific sources for project cars, I have done some research and come up with a couple of ideas as to where to look:
1.
http://www.ferrarimarketletter.com/ is a newsletter claiming to have the most Ferrari classified ads in the world (or something like that). A lot of sources all in one place.
2.Visit small classic car dealers, the little places tend to get the cars the big places look upon unkindly.
3. Contact clubs. These people will be able to give you local knowledge on sourcing what you need, which is very important.
I, sadly, can't give you much more specific information as I am halfway around the world from you, but I hope that brief bit of information helps.
Nick