The next option is to mount them above the plastic map pockets. You would have to cut a hole through the plastic and sheet metal behind it, but there would be plenty of clearance behind there for speakers to sit in. Even the later cars with speaker cut-outs may require some cutting here unless small speakers are used. The 6 ½" speaker is fairly common for front speakers (where the holes fit a 5 ¼" speaker, I believe). There are a couple of objections I have to mounting speakers here. First, they are under the dash, pointing towards your legs and the center console. Therefore one would really have to crank up the volume to hear anything. Also, late model cars have open wheel-wells which are covered by the plastic linings. If your car happens to be missing these linings, your speakers will be exposed to the elements. I can remember riding in a friend's '80 Spider, which was missing those linings, when it was raining and water would splash through the speaker holes whenever we went through a big puddle.
At one time I had some small 4" speakers mounted in the map pockets themselves. I capped off the top with some particle board. These sounded ok and provided some decent sound from the front without having to go through the trouble of cutting holes in the sheet metal. The problem was the plastic tended to vibrate at higher volumes and the little speakers couldn't put out a whole lot of low or midrange frequencies (bass). I wanted some larger speakers up front so I removed the map pockets and constructed some speaker enclosures (boxes) to take their place. I used ½" particle board and built the largest enclosure possible that didn't interfere with the hood release lever or reduce leg room significantly. I sealed them with silicone caulking and covered them with carpeting to match my interior. Then I screwed them in place where the map pockets used to be and mounted some Pioneer 6 ½" speakers in them. These provided nice volume, a fair amount of bass and very crisp sound.
At the Fiat Northwest '97 AJ Gregory showed me his custom setup and I was very impressed! In fact, it's the best setup I've seen/heard in a Spider. He created speaker "pods" from fiberglass, which mounted in place of the map pockets. These pointed the speakers at the driver & passenger. They sounded incredible! The "ideal" stereo setup creates a sound stage (where the sound seems to come from) right in front of the listener. Having the speakers pointed at you raises the sound stage up from the floor and puts it more in front of you.