If I am unsure if an engine has solid or hydraulic lifters I adjust number one exhaust as a hydraulic and run the engine to see if the engine misses or runs smooth.
If they are solids it will continue to miss.
If hydraulic it will smooth out as it bleed down to its working position.
This is best done with a warm engine as the lifters will be slow to bleed down with cold oil. With warm oil it happens almost immediately.
If you want to see visually, hydraulic lifters have a snap ring in the top to retain the piston.
