I have Bosch 7" headlamps on the outer pair of my 410, which are rounded and not flat. IF you look at somehwere like
Holdens they have an great deal of choice of 7" lights, both rounded and flat.
(I have 5.75" sealed beams in the middle, which I shall probably change to halogens as well, as the smaller sealed beams are becoming harder to find here now.)
My headlights are wired so all four run as both main and dip, through relays, which gives excellent visibility at night, but you do have to make sure all four lamps are correctly aligned to avoid dazzling other traffic.