Solid flat tappet cam
Back in the day of chebby LT-1 they had solid lifters. Had a buddy with one of those engines from a 71 vette in his 76. It sounded way cool as you can hear the valves clicking due to the valve to lifter clearance.
I don't think I would build an engine now with solid tappets and have to adjust them. Why would they move? Valve sets into the seat (closes the gap), cam/lifter/pushrod wear opens the gap.
Why bother?