I bought a 1966 Volvo 1800S - the last year with the swoop side trim.  This lovely form was designed in the late 1950s but sold through 1974.  In two years it's jumped in value. But the most undervalued classic I know of is the 1978-1979 Alfa Romeo Sport Sedan.  It handles the same as its transaxle Alfetta GTV cousin (it out-handled my 240Z on the track back in the day) but had velour seats, leg room and understated elegance.  As such, it's not the same as the earlier Alfetta Sedan. Nearly all mechanical parts are shared with the more common Alfetta GTV. Alfa sold only a few thousand Sport Sedans in the US - with no power windows, seats, locks or even steering, it wasn't an American consumer oriented car - and most have long since been scrapped; rarely have I seen one on the market, unlike other Alfas of the era.  There may be only a few hundred in the country. In other words, it's rare, it's lovely, and it's a fun Alfa.  And the last one I saw on the market, very clean, was under 20K. ... View more