So after fixing exhaust leak, the engine is making a ticking sound on the driver side of the engine?? Tried uploading video but it's not letting me.

 

If this truck has sat for a long while, something in the valve train maybe sticking. Have you changed the oil/filter lately? My 360 rattled for the first 4-5 times I started it, then it went to a slight tick. Later it stopped making any noise. Does the ticking increase in volume and speed if you increase the rpms? You could try some Marvel Mysetry Oil. You could also take that valve cover off and check the rocker arms for any excessive play then start the engine and check each one by putting slight pressure on each rocker arm to locate the noise.

 

Cut a three-foot section of old garden hose. Put one end in your ear and poke around the exhaust ports with the other end. You may find a gasket leak.
Common.

 

It wasn't making any sounds until after I had temporally patched up an exhaust leak using sealer. Removed it this morning and the ticking was gone. Why would sealing the leak cause this??

 

Sealing the exhaust can just be allowing you to hear the ticking when you remove the seal you can't hear the ticking because the leak drowns it out? Just a thought I would look at the rockers as well that would be the hope full solution otherwise it could be as bad as something broken and bouncing around somewhere. Best of luck that's never a great feeling finding something else wrong