replacing tape deck

Or, go to Google and type in 1.5 DIN - All those will directly fit into the hole in the dash for the radio.
That'll sound bad with the stock amp and other stuff though, the inputs will have too much power. I'll have a stock Monsoon CD player out of my car here soon, though...
The factory unit will plug right in of course and have all the original features including steering wheel controls and speed compensated volume. You should be able to find a used one here or on ebay (lots of people upgrade).
The Audiovox unit is the GC600 from their Special Performance Series. It is a straight plug-in replacement with both CD and cassette in one unit designed to look like a factory system. It is intended for dealer installed system upgrades but can be bought over the counter. It supports all the factory features (including steering wheel controls) except for the speed compensated volume. Audiophile snobs will tell you that Audiovox is junk but I had one in a previous car and really liked it (much better than the original Monsoon).
Another option would be to add a factory CD changer to the existing cassette system. The wiring is already in the car and you can usually find a changer fairly cheap.







