Years back when I had my Valiant, I had the same issue with it's 318. Passenger side head ticked loud cold, fairly quiet when warm. Mom said the car ticked since they drove it out of the dealership.

I didn't spend any time on the 318 heads, but swapped on a set of 360 small-valve heads and a 4 bbl intake. The ticking went away, so I can only assume it had something to do with the head.

Currently, the 304 in my AMC Hornet is doing the same thing. Passenger side ticks. All the lifters seem good so I can only assume it's the same issue as with the Valiant. Either a poorly lapped valve, or maybe an exhaust valve rotator has stuck and is wearing a valve prematurely.

I had hoped it was just an exhaust leak, but I changed all the gaskets (and don't run a heat riser) and that didn't change anything.