i have them on my 72 super:
using the 4100k bulbs and hella ballasts. they are the brightest. as you go up in numbers to 8300k the light becomes more blue/purple in colour, but your light output decreases. so the hotter the temp ____k, the more purple you'll see but the less lumens of light they will produce.
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'72 super
'65 bus
'52 split
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