I think that the main answer to your question, especially for a car which is not new like ours, is to pump in some good ol TLC to start to get back what your car may have lost over the years of her life. So my advice is to start with a FULL service so changing all of the filters and fluids, to start with, and then write everything down and run the car for at least a week and or X miles.
Then have the car fitted with a BMC or other air filter (the material rather than paper ones) to allow her to breath better. Again try her for a few days and note any changes you feel.
Then change all 8 spark plugs for new ones (again, always a top brand like NGK or similar) and see how she feels.
I would also suggest a carbon clean although the V8 engine is not noted for these problems, but probably worth it.
Etc. I think that new tyres, shocks, and stuff are all worth it when you are talking about an older car. Tuning on a normally aspirated engine is not gonna gain more than a few horses, I understand. Have fun and tell us what you do!!
