How can you tell the difference between an exhaust header gasket leak and a valve tick?

After rebuild I have a tick, worse when the engine is cold but still there when warm. Right hand bank only.

Builder thinks its the header gasket leak, but I replaced the gasket and its still there. The gasket I took out didn't have any obvious cracks or blow outs.

I tried adjusting the valves (hydraulic lifters), engine off, and it didn't help. Haven't yet tried to adjust them with engine running.

Hate to ask the next question, but how do you know if you have a cam lobe flat spot tick?

a exhaust leak can be detected with your hand you should feel the exhaust pulse against it. get a set of old valve covers and install them with the top or tops cut off and start it up. you get some splatter but the noise should be easier to detect. if checkes out then you might have a particle in the motor.

Are your rockers and adjusters stock? If so there are no "adjustments" other than the initial torque spec.

I had 4 70+ % flat intake lobes on the cam in my '69 and it had no tick and it cruised nicely, but had no top end power.

Any chance you have interference on the bottom end? Rod bolt nut to windage tray, dipstick to crankshaft, etc? Try removing the dipstick from the tube while running.