I set up the heads on my 528 Hemi and it broke in fine. I did have a problem with the 67 Vette big block with a lifter failing to pump up and it made a BIG TACK TACK TACK as it ran. Luckily, I caught it before it damaged the block but it did start to mushroom the lifter.
I'd take the valve covers off and inspect everything closely. You may even have to pull the intake to check the lifters. If its a pretty severe solid sound I wouldn't run it until you check it. Maybe since you paid somebody you can take it to them and see if they'll fix it.
If its more of a tick that a solid tack then you can adjust the lifters again and take out any excess play there might be. I adjusted mine just like the big block chevy since the cams are hydraulic with adjustable arms. You can fire it with the valve cover off and put some pressure on each rocker to see if they're loose. If they are tighten them a bit.