After 1980, all headlights installed in the US were rectangular in shape (so, technically, the ones about which you're asking *are* early 1980s, but really only for the first year of the decade).

Are you curious about the single round or the quad round (two on each side) headlights? The quad rounds can be easily installed in your car--as has been said, all you need are the headlight buckets, the lights, wiring, and frames, which all can be easily gotten from your local junkyard (if it has many 1976-1980 240s!).

The single round headlights will require a bit more work. My vote is for the quad rounds because, besides the personal bias, they theoretically provide the greatest light output out of any of the Volvo 240 headlight installations. Put in some E-codes and never look back!