Lighting
From GummyCarbs
SAE/DOT vs ECE/Euro
ECE/Euro headlights have a much sharper cut-off. DOT still mandates 20% of the light be thrown upward to illuminate road signs. Euro headlights will have a horizontal cutoff which becomes about a 45-degree upward angle to the right. This allows signs to the right to be illuminated without blinding oncoming traffic.
Sealed Beam vs H1 vs H4
Sealed beam headlights should be disregarded. They're antiquated technology, and I don't even know if the beam patterns have been updated as regulations have permitted better lighting.
H4 uses a single bulb to provide high and low beams. Euro H4 headlights will provide decent light, but it will always be a bit of a compromise since a single reflector is used for both high and low beam.
H1 uses a single bulb and a single reflector, or two bulbs and two reflectors. In theory, this allows precise aiming of each filament.
Generally speaking, a dedicated H1 high beam will give better light distribution than an H4 on high beam.
Housings
Generally, it appears that Cibie is regarded as having the best lighting pattern, then Bosch, which seems to be unavailable these days, then Hella. Hella is said to have thicker glass than Cibie. Cibie is only available in ECE/Euro configurations. Hella is available in both ECE/Euro and SAE/DOT. In general, running a non-DOT headlight is illegal in the United States. Oregon, for example, had its own lighting standards until 2001.
5-3/4 inch
Hella
The Hella catalog is available [here]. It lists the following 5-3/4" (135mm) headlights:
| Description | Part Number | Form | Single or Dual housing |
|---|---|---|---|
| 5-3/4” Round Conversion Headlamp Kit, high/low beam (ECE) | 002850811 | H4 | Dual |
| 5-3/4” Round Conversion Headlamp, high/low beam (ECE) | 002850871 | H4 | Single |
| 5-3/4” Round Conversion Headlamp Kit, high beam (ECE) | 002425811 | H1 | Dual |
| 5-3/4” Round Conversion Headlamp, high beam (ECE) | H11425011 | H1 | Single |
It appears that Susquehanna Motorsports (http://www.rallylights.com/) sells H11425011 as HL71157 (HL71156 on Amazon, for some reason). It's available on Amazon for $10 less if you search for the actual Hella part number (H11425011).
HID Conversion
Don't do HID conversion kits. Existing reflectors are not intended for HID bulbs, and HID bulbs don't appear to be engineered to properly reflect off standard halogen reflectors.
Kansas HSTA has a blog entry on the cheapest HID lighting available (4300K McCulloch G5 HID kits for $185 per pair).