Either Hella or Bosch H4 with the Hi-Power Relays & 80/100 w bulbs - BusDepot has a deal on the Bosch ones (topic on here somewhere), but Hellas from PP, Pelican, AA aren't much more dough & per the Euro spec 914s too.
USA DOT didn't allow non-sealed beam back then since GE, Westinghouse, Sylvania, etc. had strong lobbyists!
Dan - contrary to the others on here - IMHO 55/65 w are too dim at speed on a windy road or out in the country with our 914s, and with the addition of the hi-power headlight relay kits for the higher power bulbs, the stock wiring should have no problem.
Different headlights on my 88 Westy (rectangular), but the 80/100 bulbs + relays made a HUGE difference in what I could see at night!
I wished I had them in the Westy last Sept. up in Bolinas Bay area!