Interior Bulb Interchange, 6411 vs 6418 vs 578?

[SilverIris]

After some battery issues on Iris, I've decided the lighting system needs some attention to curb its current draw. Put together a list of everything needed, went to the Ebay and got stopped by conflicting info. For ease of comprehension, let's focus on the trunk lights which are #6411. Some sources such as SuperBrightLEDs say it cross-references to #578, but I'm a tad skeptical as Onyx uses those in the back seat overhead lights/hatch light (which I want to convert to LED too)

Dug around in my bulb box and found one of each. #578 has flat ends with 'looped wire' contacts, while #6411 has the typical Festoon tapered ends. Otherwise, they look the same.

So I looked further into it. Other sources say that #6418 cross-references to #6411 as well. Has anyone tried swapping a 6418 into the trunk lights? Or tried putting a 578 in there? I'm not concerned about the wattage, just whether it works or not.

[chemmech]

same question here and do led's operate safely without melting the housing from the heat? any info on good ones to get?

[SwallownAmazon]

For what it's worth, I tried LED bulbs in the trunk, interior and rear light clusters of my 1990 Audi 90 20v to give better light output and reduce current consumption/less heat output. I gave up in the end because the bulb failure warning could not be eliminated even with the ballast resistors to try and fool the thing into believing that the correct bulbs were in place.
I did the same thing for the reversing lights in the BMW with the same result so still stuck with reversing in the gloom

[PiotrC70]

Based on the ones I ordered from superbrightled's I ordered 9 of the 4410 (44mm wide) (578 type as it's stated on the receipt) and 7 of the 3710 (37mm wide). I forget which went where but I've never had issues and they are all festoon type with the tapered end. The only "issue" I had was on the trunk where I had to slightly bend one of the prongs because the light didn't feel like they snapped in well. License plate needs the canbus style to avoid lighting error when scanning the LCM.