Lark Hunter
Newly Enlightened
I'm fairly active in a few vintage car clubs, and occasionally work on or provide assistance regarding lighting on vehicles with 6 volt electrics. The 21/3cp 1154 and 1158 usually provide adequate performance if the wiring, switchgear, and grounds are up to snuff and lamps are clean and shiny or repainted inside, but there have been some instances where a bit more punch would be helpful for brakes and signals. I have used a 1680 bulb in place of an 1129 a couple times (paying mind to the significantly increased amperage), but have had zero luck finding a legitimate dual filament bulb with more than 21cp. All I've seen are those wretched bodges with two separate halogen burners, usually of obscenely high wattage, that render your lamp optically worthless; and then there's the parade of LED poop that is best suited to lighting up the bottom of a garbage can.
First choice would be an incandescent with the same L.C.L. as the original bulb (usually 1.250" for a standard S-8, right?), as it seems easier to advise a person to beef up their wiring, than it would be to ask them to evaluate an LED product and judge whether or not it will work with their given lamp's optics (and that's presuming that there's even a LED product on the market that doesn't suck).
First choice would be an incandescent with the same L.C.L. as the original bulb (usually 1.250" for a standard S-8, right?), as it seems easier to advise a person to beef up their wiring, than it would be to ask them to evaluate an LED product and judge whether or not it will work with their given lamp's optics (and that's presuming that there's even a LED product on the market that doesn't suck).