The 9004 and 9007 are not interchangeable for several reasons:

1) The filaments are in a different position, and oriented differently. The 9004 filaments are transverse to the bulb axis, and the 9007 filaments are in line with the bulb axis. This is important because the reflector and lens optics of a particular headlamp are based on specific filament position and orientations. The US headlamp beam pattern is bad enough as it is--messing with the filament orientation can only worsen it.

2) The pinout is different. The high feed, low feed and common (ground) terminals are rearranged in the 9007 compared to the 9004.

3) The keying on the base is different, so a 9007 cannot be inserted into a 9004 headlamp or vice versa.

To answer your implied question, you don't have a wattage problem, you have an objection to the US beam pattern, which doesn't generally do a very good job of lighting up the foreground (road near the vehicle) and which tends to produce a narrow, rather dim tunnel of light on the road with a "black hole" directly in front of the car. European headlamp beams don't have this deficiency at all, but US regulators at NHTSA like to pretend they know better than the rest of the world, so we're stuck with this kind of junk unless we're rich (to install the very expensive, but very good '86-'93 240 European lamp assemblies) or own a car with sealed beams that can easily and economically be converted to European (H4 type) headlamps. "ten more watts" would not help your headlamps a bit. 100/80w 9004s wouldn't either, for electrical, mechanical and optical reasons which you can read all about at

http://lighting.mbz.org/faq in the "overwattage bulb" section.

If you're interested in more information about all of the different bulbs used in headlamps and fog lamps, I've put up a comprehensive chart at http://lighting.mbz.org/tech/info

--Daniel Stern

Stern Automotive Lighting Consultation

http://lighting.mbz.org/tech