Lighting

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) (note: the H11425011 says it doesn't include a bulb, which is in keeping with the Hella catalog... So maybe ralleylights.com is the best option... Okay, well, a [http://www.amazon.com/HELLA-H1-100W-Halogen-Bulb/dp/B0002M9URU/ 100W H1 bulb is available for $7.42, so the non-Susquehanna Motorsports option is still best)

Bulbs

H1

The Hella catalog lists H1 55w 12V p/n H83115001 (DOT) and H1 55w Hb3115002 (DOT) "High Performance Xenon Blue"

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).