As far as modifications go, I haven't done too much mechanically, any small mods have taken the car back to nearly stock. Stock air filter and Carb, I removed the AC condenser and all of the AC parts, it wasn't working and I didn't like carrying around that added weight.
On the interior, my original AM/FM radio died last winter so I installed a JVC KD Sx-980 MP3 Player into my Glovebox. The deck is held in place by a solid maple housing inside the glovebox.

Underneath the dash I installed two 3 1/2" speakers into the original brackets. In the trunk went two 6X9's into the orginal brakets. The effect is a 200Watt Mp3 sound system that looks totally stock, and doesn't ruin the classic car look. While not the largest stero or coolest, it can still kick out the volume pretty well.
The interior is near mint, with no cracks or rips in the seats or dash, this is the ORIGINAL interior. The Bucket seats,long floor console that slants towards the driver and that wild concave dashboard finish off an interior that is as original as the exterior.