Annoying ticking noise/Kind of a Metal on Metal Noise

[1974ChevyC10]

ok another thing has sprung up on my truck but i feel its minor.on startup,while sitting at idle,coming to a stop my truck makes this what i call a ticking noise-it sounds kinda like metal slapping against metal.it does it too off and on while im driving but you can barely hear it.i took my convertor cover off b/c it was bent and rattled like hell and was very annoying to me and the truck is a little quiter now but it still has this annoying tick.checked the convertor bolts and they all seem to be there,watched the convertor while the vehicle was on and it seems to be spinning true and doesnt look like its out of round or missing a bolt.the oil level in the motor is good.i even checked the harmonic balancer to see if it was ok b/c i had this problem once with a vehicle and it was the harmonic balancer at fault and in this case it seemed to be ok-no odd noises there and when it went on one of my old vehicles it was loud as hell no matter what.i think it may be a bad collector gasket but i may be wrong here.any ideas guys.