Mine was complete when I bought it (been stood 10 years in an old fella's garage waiting for restoration). I did think about tidying it up and putting it back on the road with patina but, not knowing anything about its history, ended up as pretty much a nut and bolt resto. The frame and ancillaries were powder coated. Tank, oil tank, toolbox and mudguards were painted. Rechromed, fasteners zinc plated, wheels rebuilt with new rims and s/s spokes, engine rebuilt (twice because an idiot called RM fooked up the first one). All in all, spend around £4.5k on it (not including the second engine rebuild), but because I bought the bike originally for a breathtaking £950, it meant I could splash out a bit on it.
There's probably enough bits and pieces lying around in members' garages to build at least one machine from scratch.