annoying ticking/tapping noise

Hey guys,

I have a 1971 nova ss that I just got done restoring. It has a mildly built 350 and a th350 trans. its the original engine and transmission with 67000 original miles on it... to cut to the chase, the car performs great, the engine runs strong, etc. but there is just one problem I am having that really annoys me..... there is a sort of ticking noise coming from the drivers side of the engine when I get up to around 40-45 mph. it does it most of the time when I stay at a constant speed, but most of the time ill accelerate up to about 40-45, then let of the gas and it will sound really start ticking while im costing, then it eventually goes away... at first I thought it was a small leak when I installed my new headers but after I figured out that wasn't the problem, my dad said it could be a valve or something and the headers could be amplifying it. I don't really think its a big deal, because the car runs great and strong, but I would just like to know what it is, or if anyone else has experienced anything like this...

thanks in advance,