Text and photos by Barry Lee Brisco
356 headlights are not known for the luminousity (though in their day they clearly outclassed any British sports car!) but improvement is relatively easy to come by. The combination of H4 bulbs along with Joe Leoni's HLr kit (particularly advantageous in T5/T6 models with the headlight dimmer function on the steering column) can more than double the light output compared to the stock system. This is well worth doing to any 356 that gets much night use, or for those who like the idea of running headlights during the day for extra safety
Installing the Leoni HLr kit is easy, and the instructions provided are very clear. In T5 and earlier cars, removing the glove box first is essential (T6 cars have the fuse box in the trunk and this description and photos don't apply). This is readily done by removing the screw that is visible just above the glovebox door hinge when the door is opened. No need to remove the upper screw. The only difficulty I had was pulling the long gray wire forward through the fuse tray and center tunnel up to the battery. These areas are packed with wiring and the flexible gray wire probably can't be pushed through without assistance. In such cases, employ an old electrician's trick (described to me by several helpful 356Talk members) know as the "come along". Cut an 18" length of fairly stiff wire, or an old coat hanger, and tightly hook one end through the ring terminal at the end of the gray wire. Bend the other end back so it doesn't cut into the insulation of the existing wiring, then push it through. Any extra gray wire can be hidden behind the top edge of the floor mat next to the tunnel.
One other thing to pay attention to: position the new relay pair as high as possible above the fuse box, just below the wiring bundle that runs off to the right (see photos below, taken in a T2 coupe). In that location, when your drill punches through the firewall you won't hit the gas tank (not an issue in T6 cars since the fuses and relays are in the trunk well above the gas tank). The new relays are now hidden behind the glove box.
The end result is significantly brighter headlights than the stock setup. You can easily double the brightness by installing modern H4 bulbs, which the stock system cannot handle due to their current requirements. These bulbs can be purchased from the suppliers listed at the bottom of this page, but be sure and check what kind of headlight assemblies you have first: one type allows just the bulb to be replaced, another has the bulb sealed into the unit. You probably won't be able to tell which type you have without pulling one out of the headlight bucket and looking at the back of it. The HLr kit works with all types of 356 headlight assemblies.
This list of vendors, in alphabetical order, is not necessarily comprehensive, and additional companies may also offer similar products. Note that where possible, links are provided directly to a specific product page if available.
356 Electrics: headlight relay, H4 bulbs
NLA: H4 bulbs
Zim's Autotechnik: H4 bulbs