Progressively worse ticking....
 

For some odd reason I have picked up a ticking noise coming from the rear end of the drivers side head. I noticed it a few weeks ago, but now it has progressively gotten louder where it's impossible not to hear it, even over the flowmasters. They are the stock heads- could I have a bad valve or valve spring? The car seems to run fine, no changes in oil consumption, MPG, ect... Do you think I need new heads??

Rip off the valve cover and take a look. Could be a loose rocker, or a rocker has loosened to the point that it's not holding the pushrod down, causing the pushrod to shoot up into the valve cover. Could be a number of things, but you need to check it out to find the problem.
Dave

Have you added aftermarket headers to the car? If so, you may have burnt through the header gasket.

i think the reason for you ticking is possibly a colapsed lifter