Adjustable or Non-Adjustable rockers for '70 Mach 1 428SCJ

I am torn what to do with the rocker arm/ shaft setup for my 1970 Mach1 428SCJ restoration.

The car is put back pretty much to its original standard and the motor/trans are original. The motor was said to have been rebuilt 15 years ago but just sat with no oil in it. I took it to a local motor shop to have them take a look, they didn't take it completely apart but said it appears rebuilt. We completed the restoration in 2017 and had no issues until around 280 miles where a slight ticking appeared. We took the valve covers off and detected the ticking seems to be coming from the lifters. Some push rods spin freely and others don't spin at all. None of the rocker arms move at all when you try to manipulate them except for cylinder 1 which moves quite a bit and it also is where most of the noise comes from. Because its a 428SCJ they are hydraulic lifters and non-adjustable. I question the integrity of the rebuild so I took out the pushrods and lifters. I've attached some pictures. I have no interest in adding horsepower to the car or race it. The car is driven as a cruiser.

I saw a few fellow owners put Harland Sharp roller rockers in but they seem to be race-oriented and some people said they had trouble fitting the original valve cover on with those. What are some of your opinions on the Pro's Con's of adjustable vs non-adjustable and what brand would prefer? Thanks to everyone for the insight!
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