Ever since I have owned the Pk Ave I have been using CD'* and wanted a line in.
Luckily the OEM CD Radio had a cassette player...

So today I found a Cassette line in adapter ( how modern)

Now with a line in, I can officially get modern with a new 4 Gig MP3 player !

The small walkman player has bass boost & does quite well.
Supposedly you get 15 -18 hours out of one charge on the USB Mp3 unit.
Finally I don't need to be looking for cd'* all the time now!

I've been digging 'cuz I know I still have one of those suckers somewhere because my unit is like yours with both CD & cassette. I like the Bose system and would rather not screw with a stereo upgrade for now. How much is the little Sony unit?

OMG, do they still make those? I thought they went obsolete when they stopped making tapes.

^ LoL
Ya Luckily for my modern system... they still make them..Ha ha..

Stephen, Just do a local google search for Sony NWZ-B173F ..I think it was $35 here..
It is also easy to use, comes formatted, and w/windows explorer just drop your mp3'* into the players music folder & done. It also has FM & voice record etc..

Thanks for the trip through the way-back machine Art.
Glad you figured out a way to use an MP3 player with the old unit, how does it sound though?
I have heard the volume is a bit low compared to the CD Player, but I guess if the volume of the MP3 unit is up a bit it should still sound ok.

A tip, don't leave that tape adapter in there all the time, especially during the hotter months of the year, also once and a while after long usage I'd eject the cassette adapter and make sure it is not getting too hot, you do not want it to warp in there.

Some good tips William on the adapter use. I generally always eject it after use. It does get warm for sure.
The Sony mp3 has an exceptional output. Louder than a cd actually. I had to turn down the mp3 player volume from max output. Especially on higher quality mp3'*
One annoyance I have noted is that the main round dial flashes to the music and is too bright at night/distracting. May make a tape cover for it as there seems to be no way to turn off the dial lighting.
Here is a photo that shows how compact this mp3 really is.

And one showing the removable USB cap along side a compact accessory USB adapter.

Nice, that is pretty compact!
Is that a back up camera you have installed?

I have been using my I-phone as a MP3 player, it was easy for me to add the line in for it since I have an aftermarket Pioneer deck though, I just used the connector that is supposed to go to a CD Changer, I stuff the wire where you have the MP3 player, good use of that little cubby hole.
You may want to find something to help it fit a little tighter in there, so it does not fall out and get under your feet while driving, maybe a little cloth above and below it.
that should work well as long as the mp3 player does not heat up a lot, I don't think that it should get too warm..

No William that is a forward facing wide angle 1080p DVR (Dash Cam) with sound.
Mounts with suction cup, so I can move it between Vehicles.
The mp3 has a tie clip on it and I can clip it to the wire coming out of the cig socket that powers the dash cam...
I put it in the tray for illustration only. Or you can clip it to your shirt too...I do that now sometimes to make it easy to forward a track.
Nice to have a Pioneer deck with line input.
Removing the factory deck on the 97+ OEM radios are a big deal and according to Jason'* link I viewed -
required carving of the dash interior a bit to fit in a 1DIN Head unit...no fun I am sure.
I'll make do with what I now have for a while..

you have to cut the plastic out of most gms, not a big deal. i used a dremel. the aftermarket units are a million times better in every respect, i can play mp3s on a usb stick that is under the dash or on my phone via bluetooth, i can put as many on that as i want to (whatever micro usb card you want) and it auto syncs my android phone, brings up the player and starts on its own. no wires, no buttons, way better sound