I would check to see if those "ratty old headers" were tight.Exhaust leaks can sound like a lifter ticking
Jeff

 

+1 exhaust leaks have the same ticking noise as a loose lifter.

 

soaring is right, could be exhaust. if its a lifter it could be a couple things

a) out of adjustment
b) stuck from being gummed up inside with nasty oil
c) broken guts in the lifter

roller cams and lifters can be reused and mix matched cause they wont have any significant wear and there is no taper on the cam lobes.

a flat tappet cam has a very slight taper on the lobes which is what makes the lifters rotate. if the lifters didnt rotate they would wear out almost immediately.

lastly, i have always been told by reliable sources (fellow machinists) that you CAN use a new lifter with a used cam, as long as the cam still has its taper and isnt destroyed, and you use cam lube on the new lifter.

 

I put new gaskets on it three times allready also collector gaskets. I bought new headers but I dont want install since I am going to engine swap soon. One tube has been almost smashed shut to clear the firewall. Some definite hack work went on from the pravious owner..I a going to go with rmp mounts on the cleveland as long they will work