340 issue after camshaft change

If, as you say, you spun the engine over and it had no compression, AND the valves are not closing;
what are the chances that every valve kissed the piston, and now all or at least half the valves are bent.

At this stage I would remove the rocker shafts and do a LeakDown test to see if you still have an engine.

if you do;
then I would find split-overlap and see if the cam is installed remotely close to correctly.

After that we can work on the lifter preload.