I just bought a 2000FC and it came with the 80/2.8 Planar F lens. They stuck a 58mm on the front of the lens but I don't think it's the right one as it doesn't really fit properly.
I've searched high and low to find the filter spec for that lens and can't find it. Does anyone know the size? Note, it's the F lens, not CF or FE.
Don't know the lens first hand but according to this data sheet (http://www.hasselbladhistorical.eu/pdf/lds/F80.pdf) it has a standard bayonet 50 mount. Filters for that mount are widely available and not as expensive as some other mounts. Alternatively you can buy a cheap bay 50 to 58mm adapter from ebay.