im chasing an alternator on ebay for my EL ghia at the moment which is a good price and looks and sounds to be in good condition. My only issue is the seller says he cant tell if its an EF or EL alternator as the sticker has come off. Is there a difference between the two and are they interchangeable? I recall seeing that EF is 110amp and El is 100 amp or somethign along those lines. Is this the case?

Yes, Ef and El alternators are interchangeable. If you buy a new Bosch 108amp alternator the part number is the same for EF,El.