HH56 wrote:
Did you look at the head to make sure one or more valves was not hitting the top of the combustion chamber. That can happen if head was milled a tiny smidge too much.

Have you verified the oil filler tube is inserted correctly and a counterweight is not lightly tapping the baffle plate. While the noise would be coming from the other side and be very repetitive with crank rotation, it can sound like a lifter under the right circumstances.