i have a 93 lumina eurosport with 190,000. When warmed up and held at about 1200 to 1500 rpm it clearly has a loud and hard clank emitting from the tranny it also wants to knock itself out of park at the same time. No other apparent problems with tranny shifts and drives fine. Could this possibly be the convertor or something internal such as worn parking pawl?

Make sure your linkage is adjusted properly. It sounds like when the shifter is in park, it's actually between gears, and when RPM raises and trans line pressure increases, it's forcing the piston into gear and clanking against the parking pawl. Make sure you don't do this with your foot off the brake, or you could have a nasty accident if the car jumps in gear and the pawl lets go.

When you rev the engine up in park or Neutral the 2-1 kick down band will sometimes will grab usually it around 2000/2500 RPM. That will make a quick thud and jerk the car. It also could be the low sprag but that should also do it while driving. My 95 GP would do it even after an overhaul and spreading out the band.