Bicycle Mechanics - Component group for older bicycle

I have a couple bicycle related questions....I hope to get some answers to.

I purchased in the mid 80's a Japanese made Panasonic 12 speed road bike. To this day I ride it and it is excellent shape for being 20 plus years old. I do around 50 to 75 miles per week riding.

Aside from the normal wear and tear and the parts just getting worn due to the age of the bike, the frame is in excellent shape and am interested in doing a complete component overhaul and possible upgrade.

I am in the beginning process of looking for components and parts that would fit this bike. I have yet to find anyone selling Panasonic parts.

Is it possible to use a universal component group package or is there a a different bike brand that would be interchangeable and fit this bike?

I plan to have the frame repainted and make this restoration a winter project.

I appreciate any input.

Thanks

I have one complete rebuild under my belt. It was also a 80's vintage bike. So, from my limited experience, here's my take on it:
If you intend to replace ALL compoenents, you won't encounter the compatability issue. For instance, if you decided to make your bike a modern 18 speed, you can slightly spread the drop outs (best done by a bike shop) to accomodate a new 130mm 9 speed wheel. The entire drive train can be replaced with a solid Shimano 105 set with down tube indexed shifters. This would also include replacing the bottom bracket.
Your brake levers would most likely be reusable. Or, you can replace with new for about $50. The brakes themselves could be reused or replaced depending on how much of a restoration your doing and the thickness of your wallet. Good luck!

I should add that for all of my components when I did my rebuild, I spent approximately $1200. The parts were all from online shops such as Performance and Nashbar. This includes a wheel set and mostly and components that are about 65%DuraAce a little 105 and a smidgen of Ultegra. The bottom bracket was installed by a bike shop as was the new headset. I also had the bike shop spread the frame for the new wider wheels. The bike was stripped and powder coated in black. It had all new manufacture's decals made up by a sign shop.

As Don makes clear...
It's way too easy to rack up serious money bringing an old
bike back to life. If I had realised how much my Fuji commuter project was going to wind up costing; I would have put that money
towards a new bike.

Parts?

http://search.ebay.com/panasonic-road-bike_W0QQsokeywordredirectZ1QQfromZR8