OK, poked around a bit more on EPC this morning. Initially, when I looked up the "Interior Lamps" section, even EPC indicated that there were two festoon style bulbs in the overhead console!
But when I backed out of that menu and looked at all the categories under "Electrical System", I noticed that there was a "Note" icon next to the Interior Lamps category. when I clicked on that note, it said "Interior Light Bulb: The correct Bulb for the Interior Light is A002 544 38 94". Hmm.
After doing some more Googling, it looks like that the Sylvania 2721 wedge-style bulb (not a bayonet as I originally thought) is the generic substitute bulb for that MB part. BUT, it turns out that this bulb is only a 1.2W bulb, which clearly isn't right. So perhaps that note is really referring to "instrument panel light" rather than a "dome light".
I really wanted to have the new bulbs in hand before I started to take things apart AGAIN. I just had this all apart yesterday to replace my rearview mirror...didn't think I'd need to drop the console to replace the bulbs, or I would've done it while the whole top trim piece was off. But since I can't figure out the replacement bulbs, once more into the breach...
I had already carefully removed the (brittle) plastic outer lens and the two diffusers inside. To remove the diffusers, I used a small flat head screw driver to disengage the retaining clip "tang" from the slot, while gently giving a wriggle & a tug on the thicker part of the diffuser shank with a pair of needle nose pliers. If you do this carefully you should be able to get the diffusers out without breaking them.
After removing the two Phillps head screws and unclipping the bottom of the console from the trim, it still wasn't dropping down. I figured out that there were two metal clips that are attached to the console that grab on to the inside of the trim piece. By moving the now loose console around a bit, I was able to maneuver the tip of a plastic trim tool underneath the left metal clip & got it to disengage from the trim piece. Once I did that, I was able to slide the console down and to the left to get the other metal clip to disengage. There's also a wiring harness on the right side of the console, so it has to be removed at a downward angle. You can sort of see where the metal clip is in this poorly-lit photo.
Here's the light console once it's free from the trim:
Once I had the console hanging down, the bulb retainers are clearly visible. The one on the right side was no problem, it gently twisted right out. Here is is picture of the bulb and the retainer.
The left side was a little more difficult. You can see in the photo above that there is a five or six wire wiring harness that's rather tightly wrapped around this bulb retainer that must be unclipped & moved out of the way in order to remove that bulb. When I got that harness out of the way, I noticed that this bulb retainer was much more loose than the one on the right. My guess is that harness being so tightly wrapped around it puts enough stress on the assembly to cause it to cold flow out of shape over time. This could explain why so many of us have problems with this bulb flickering on and off while the other side doesn't seem to have that problem.
Here is the bulb & retainer out of the console:
Anyway, I took both the bulb and the retainer to AutoZone to see if I could match up the bulb, since the only markings on it were "12V 6W". Looking through the racks at AutoZone, it appears that many of the "three digit" bulbs are all roughly the same size and all have the same wedge base as the dome light bulb. After looking through a couple different packs, I decided that the type 194 bulb was a pretty close match.
However, I had decided that if I could find an LED replacement that I would go with that instead of an incandescent bulb. I found the "Jam Strait Amber LED Bulb" AutoZone # 343445, type 194A that looked like it would work. I test-fitted the LED base in the retainer before I left the store & it fit in the retainer with no problem. So I guess the lesson learned from this part is that, despite what it says on EPC, a type 194 bulb is a substitute for the dome light for the facelift R170s.
Here is the LED replacement:
When I got back home, the bulbs fit fine & worked when I test fitted them before re-assembling the light console. As I expected, the left light was now a little intermittent (didn't have this problem before I took it apart, but I've had it on a previous R170). When I wrapped that wiring harness back around the bulb retainer, it seems to have tightened things up enough that the bulb would no longer flicker when I tapped on the console. I'm hoping it will stay that way.
Everything went back together in reverse order with no problems. Just remember to insert the right hand side of the console (with the wiring harness sticking out) into the opening first. Then the top metal clips will engage with the top trim piece, and the bottom plastic clips last.
When I had this apart yesterday for the rearview fix I noticed that the screw opening on the left side of the lighting console was cracked (it was like that before I even started taking anything apart). I was afraid that the screw head would slip through the crack when I tightened it back up. I didn't have any super glue handy, but I did have a small washer that was just large enough to fit in the hole and provide some extra support around the cracked area.
Here are some shots of the finished product using my crappy iPhone camera. The are billed on the packaging as "hyper bright", but IMHO they are roughly the same brightness as the bulbs, in fact maybe a little dimmer. No problems with the dashboard "lite-out" indicator.