I know what you're asking, yes small round headlamps will fit in the fog location HOWEVER you need to index the metal backing plate for the light so the mounting tabs meet up and keep the lense level, the fog light mounting tabs are different by about 30 degrees, same spacing for the tabs. I am going to install some nice H1 bulb high beams in place of the fog lights, with relays etc and add some Bosch fogs below the front bumper still using the factory headlight switch. I will post a pic with the high beam conversion and indexing of the backing plate once attempted later this week, it is easily done I have worked on a few with this modification. I love the eurolights, however just more then I can budget and am already sitting on the other parts off old cars I used to own.
Just so you know it is illegal to run more then two low beam headlights in north america, the extra light source can only be fogs or high beams for a max of 4 lights nothing more.