HELP: bad noise from my engine????????

Well I have a "rapping" noise coming from my 351w roller motor, in my 67 GT.

I took her out last week and did some fairly hard runs with a buddy.....bounced it off the rev limiter at 6000rpms on one run.

Any way, I started to get a rattle that I thought was my exhaust pipes....it would appear at about 2500 rpm....not before.

I parked it in the garage.

Finally I had a look at the car, pulled the valve covers....all my roller rockers look great???

Any way, now when I start it up I immediately get a rapping that sounds like you are banging two fence pipes together.....and if I put my hand on the driver's valve cover...it transmits a knock to my hand in synch with the noise!

So: What do you think:
1) Bent Valve
2) Bad roller lifter
3) Worse


Motor has:
Stock rods with ARP waveloc bolts
Stock Roller Lifters
Stock pistons
Edelbrock RPM heads
Speed Pro Roller Rockers
Trick Flow CroMoly Push Rods
Ford Racing double roller chain set
Duraspark Dist
MSD 6AL

I am going to pull my intake and hopefully it is a bad lifter.