I know there is a zerk fitting on the stock upper control arm but it's a dummy zerk you can't and grease to. My question is if I put a greasable zerk fitting can I grease them that way?

 

No. That's not a zerk fitting. Its a ball mount for some option your truck doesn't have. You could put a zerk fitting there, but, all you would accomplish is filling the control arm with grease. (and it would take a LOT.) None of it would make it to the bushing.

 

yep. its the mount for the air suspension ride height sensor. you will do more harm trying to add a grease fitting. When the grease for life part wears out (and that could be a long time) replace it with a greaseable part.
when the grease fittings are present...1/2 the time the lube techs don't grease them anyways. I'm the only one at my shop that has a needle to grease the double cardan joints on the 2500 to 5500..sad