good question....
i started doing research on the follies and pitfalls of the GMT400 platform AFTER my brother found the truck for me......before getting my brand new '15 Harley i never had a vehicle with replaceable bulbs. Harley had come out with their own take on LED lighting, which was like Star Trek in my mind.......and i was sold on it after riding with a guy on a moonless night in upper Vermont. i was the old dog willing to learn a new trick or three.
ok....that's when i started experimenting with the new LED tech.....and after a considerable expenditure of funds, i came to understand that stock headlight buckets were not designed to reflect the pattern of LED bulbs....i have picture or two somewhere......this led me on a quest for a "better" halogen bulb that WOULD work...the halogen has a MUCH better light pattern, though yellowish ..and i've come to the conclusion that as long as the filament is the basically the same length and width it should perform well in the lens housing.
i just read a little article about that exact substitution you've brought up......and i don't see why it wouldn't be a good upgrade. what i DID want to do is upgrade the system with relatively stock or aftermarket parts keeping close to the original design and bulb schedule.....my goal was to show a real difference without straying from "stock" configuration......the biggest thing was i didn't want another plastic headlight assembly.....
i posted about this HIR bulb when i first joined up here, my research had begun:
http://www.gmt400.com/threads/researching-headlights-gave-me-a-headache.33362/
after i get this show on the road i'll be open to reasonable upgrades if this falls short of my expectations....
i really think this should be fine.....the bulbs are still DOT compliant, "whiter" as per the kelvin scale, and they do look more modern without that European alien lens combo i've seen......i'm stuck on stock-like.....all my bikes follow very close to stock with huge improvements in engine and braking, lighting now too.
don't forget.....my plastic lenses are old, yellowed and not clear anymore.....the bulbs are old i'd guess and bulbs get dimmer over time....that alone will make it work like crap.....not to mention the fact that this system is hobbled by the fact power is taken directly from the switch and the full lumens potential can not be realized....and that was from General Motors.
if you have some patience drewcrew, what i do may give you some options.....but those newer bulbs are not the same as the original Toshiba HIR's.... that's another reason i didn't go that route just yet.....but at $24 for 2, it's not a huge waste to try......these Philips i got will not have OEM life expectancy......but that's something i'm willing to trade if it works well.
i do 95% of my distance driving at night....i like the solitude and traffic is not an issue.......alone on the road, able to see good in front of me and some good music make me really enjoy driving when i can't be on my bike.
later,
Bill