Well I could make a new thread or add to this one. I'm adding my input here, since I used info in this thread for my work.

I replaced my left rear speaker today. Hopefully tomorrow I'll get the right rear done. Notes:

-Stock clarion speakers were completely destroyed. The foam surround had disintegrated. The pressed cardboard that it was affixed to was broken/destroyed. The speaker WAS working...but clearly not very well. No stock speaker is going to take 20 years of use very well. The stock plug on the speakers does NOT have to be cut. It actually is just a plastic surround with clips holding standard-fit speaker plugs. I mangled the crud out of it until it relinquished the aforementioned metal speaker plugs, and discarded the useless plastic.

-I put in 6.75" Pioneers. Coax, not component. I would NOT recommend anything larger--unless you plan on getting super-creative with the stock mount bracket & mount height/depth issues). Even the 6.75" were...interesting. I used the same method, kept the stock/drilled hole in one corner, traced out/drilled the other 3. Be very careful not to cut into the curved metal edge as you're enlarging the hole--unless you want the mount bracket to be flimsier.

-My speakers had about .5" additional depth over the stock speakers (2.5" vs. 2" appx). That's a huge deal, and it meant that i would not be able to fit the mount bracket back onto the mount holes in the frame--unless i did some fancy bending of the bracket/etc. Instead, I opted for jury-rig method #2. My speakers came with trim rings (as most speakers do), and luckily I had not actually used the ones for the front 6.75". Here's where I got creative. I got some self-adhesive rubber friction pads (the kind you can put on furniture legs so they don't slide). These aren't very thick, but they also don't compress much. The ones I used were circular, about 1" diameter. Similar to this image:



I placed the sticky side of these on the mount bracket close to (but not overtop of) the mount holes I'd drilled for the new speakers. This allowed me a "gap". Next I took one of the optional trim rings and placed 1 over each area where the screws would go, taking care to pre-drill a hole for the screw (not required, but does make it a bit more visible where I'm supposed to put the screws). Lastly, I took the second trim ring and put the speaker on top of it, aligned the 2nd trim ring with the 1st--and both with the mount bracket. Carefully I bolted it in, one at a time, working back and forth so it would be even and not overtorqued. If you're confused what a trim ring looks like here's a sample (these are not the kind that came with my pioneers).



The net effect was to raise the mount surface height and to reduce the mount surface depth. It worked. I took additional rubber pads & some self-adhesive weatherstripping and did the best I could to insulate/cushion the speaker magnet from the sheet-metal (I don't want buzzing/vibration). I'll have to go back tomorrow and wrap the entire jury-rig mount with electrical tape to make it look better and to (marginally) improve speaker operation. (I know, I know, no stock mount ever was ideally suited as a ported-speaker-enclosure).

-Mother of god this is a frustrating experience without taking out the seatbelts. I unbolted the rear's floor mount. But really the bracket rail for the front seatbelt is keeps the front panel attached on that end, and I REALLY didn't want to unbolt it. If you do unbolt that--however--this operation becomes very elementary because then you can remove the ENTIRE interior panel. Don't even THINK about trying to do this with the rear seats in place, even folded forward, imho.

-Needle-nose pliars seemed to do the trick when a christmas-tree-plug decided to stay in the frame rather than on the interior panel. Grip the plug on the end (where it would normally slide into the panel. Then apply outward pressure as you kind of pivot the pliars in a circular fashion (not rotating the pliars). Miraculously, I didn't break any of these plugs...though some are worse for wear, as expected. I would love to know if/where I can just buy a bag of 50 or so and never think about it again. I did manage to lose the forward-most plug (the one just above the front seatbelt). It went flying when i tried to pop off the plug cover.

--The grille on the panel has to be modified extensively. First, there's a surround that extends out from the grille (towards the speaker). I presume this is to "guide" the speaker sound through the grille--since the stock speakers are so tiny. However, this extends out quite a bit and would clearly interfere with raised-surface mount like I'm using. Fortunately, it is held in place by a single screw and some small push-on type fasteners (similar to the kind that hold on the plastic panel on USDM models where the backup camera is on JDM models). Second, there's webbing on the inside of the speaker grille. Unlike in some cars, this webbing appears to be part of the body panel. This makes it all the more frustrating for removing it. Now I cannot verify the necessity of cutting out this webbing (I removed mine). I'll try experimenting on the passenger side to see if it creates interference. Additionally, if you wish to remove the cloth on the inside of the speaker grille, you will most likely have to remove the webbing. Of course, you can try unbending the tabs on the metal mesh and remove it and pull the cloth out that way. (Again, I may try this on the passenger side). I'm leaning towards replacing the cloth on mine..since the speakers just look "off" and not centered on the grille. This should also cut down on ambient dust getting inside.

Murderously hot outside, and I'm dog tired. Apologies for the lack of pictures.