Sounds like top end to me
Having heard the sound a 'ticking' kind of sound I suspect it is more likely coming from the top of the motor.
We triple checked everything when putting it back in so unless we got the tappet adjustment wrong something is possibly loose.
Maybe wrong valve caps? The original ones were flat the new ones were rounded...
Any further ideas?
Maybe BrendanB can post a link to the sound recording of the motor. Suggested he listen to the noise again and determine if its coming from the top of the motor or not. (use a screwdriver against the motor trick)