For the price difference between long and short, I don't think it's worth putting any more $$ into diagnosing whether the rings or valves are culprit.
Ayuh,... It's entriely Possible a simple Valve Job,+ fresh headgasket set could Fix the motor....
But,....
If you're 'ell bent on Throwing your money around,...
Buy a New Vortec motor,+ you'll get the Best that's currently available....
My brother (the family mechanic) seems to think I should do the wet and leakdown before throwing my money at the unknown...