Could a head gasket cause a tapping?

[Michael Smith]

This may be a little long but trying to give as much info as possible. Well just got a forged piston short block from central coast mustang. Put Edelbrock 6037's with Fel pro 10112 head gaskets, a B303 cam, FMS hydro roller lifters, stock length FMS push rods, FMS pedestal 1.6 roller rockers, and 24 injectors. Well after getting it all together I prime the pump and oil is getting to the valve train. Finish it up start her and I got this tapping so I go to the rockers and play the shim game. Tapping stops on passenger side but still got it on driver side so I switch the rockers to the other side and still got tapping on driver side. I am starting to wonder if I got a bad lifter even if they are new or when I put the driver side head gasket on I had a little problem getting it to stay in place since I have the 7/16 head bolts and it would drop down and expose itself in the top of the cylinder I dont think it did but there is always the chance that it did. Any way the tapping is driving me crazy or is it just the rockers being normaly loud? Any help would be great.
Thanks
Mike