Where do I start?

Kinda weird, backing off on the preload could make it noisy and lose some duration and lift. Not tragic. Too much preload could hold the valve open. That you would notice! What cam and Ignition is in it?
I ordered a 68 340 4 speed cam that Oregon Cam Grinders made for me. Great guy named Ken took care of me. FABO member krazycuda recommended them and has helped them by sending them an original cam for the specs to use. They also supplied the hydraulic lifters. Took a couple weeks to get to me in the east coast but well worth the wait for sure. I'm not sure what has been done to the bottom end of my engine in the cars 50+ years of the existence and it had adjustable rockers with hyd lifters previously. I debated going back to original rockers but was swayed to keep them from another FABO member. Glad I did or I wouldn't have learned how to adjust them. The ignition in the car is Mopar electronic ignition with an orange box and an MSD Blaster 2 coil.