It looks like those adjustable lifters are missing the lock nut?

The HLA’s may have 0 lash but they should be easily depressed with your finger if you properly bleed them before installation.

You should adjust the adjustable lifters down until the rocker arm has play in it. At this point, adjust them up to achieve 0 lash. If you have the lifters adjusted to far up, you risk holding the valve open and causing contact between the piston and valve. If you are checking for piston to valve clearance (which I hope you are) a lifter that is not properly adjusted will give you false readings.

Do you have lighter springs installed on those two lobes? If so, it makes removing the rocker and lifter a breeze to adjust for 0 lash. Hope this helps.

Don't turn that motor over. I'm with Beaver on this and experienced it myself. I let my lifters soak and new nothing about "bleeding" them. Resulted in quite a few bent valves. Did you bleed your lifters??

Bleed them and before starting it remove the fuel pump relay and crank the engine to lubricate it before you turn it on.