How can I tell if my small block 350 motor has solid or hydraulic lifters? Can I tell by just pulling the valve covers or do I need to pull the intake manifold?

Solid lifters are very rare these days. Usually can tell by the sound, you'll hear a uniform ticking sound from all the lifters, pretty distinctive. Hydraulics are generally quiet. A slow tapping sound that maybe goes away with engine speed is a loose or bad hydraulic lifter.