I replaced all the speakers including the deck and it works wonderfully. Of course if you want to stay original, then this may not be what you want. For the door speakers, I used Alpine Type S, 5 1/4". The opening is meant for a 4" speaker, but centering it just perfect will do the trick. Screws will obviously end up outside the original fittings, but the outer cover will cover it perfectly. I struggled a bit since the cover lay over the leather seam near the speaker, I just had to force it outside so it didn't lay on top of it. Alpine does have 4" speakers, but I was going for max RMS, something a 4" speaker just cannot provide.

As to the woofers in the back, I don't use them. I use two Type R 12" subs in the trunk. It all works out really well.

Here are the little bad things about this setup;
1.If the front seats are reclined all the way back, they come in contact with the speakers' covers, and makes a rubbing noise, but no harm.
2. Having subs in the trunk doesn't work really well for this car, since the fuel tank is right behind the rear seats and there's a firewall right there.
3. Had to remove two seals from the firewall(ending up with two 3" holes there), and remove all the sound insulation to get some bass in the car.
4. A significant percentage of bass stays in the trunk because of the firewall.
5. Running cables from trunk for battery or amplifier, to the front is quite a task. Once that is accomplished, another task lies to be able to hide it all throughout the car.

Hope this helps in any way.