05'  F150  we 'inherited'   last summer    with 218k miles  is  basically a gopher vehicle. 
As bad as the body rust is,   the noisy valve train,    I'm not sure  we'll put a dime into it to keep it long term.

Looks like about  700 bucks to  delete the  cam phaser issue..  'locked'  cam gears  plus the  computer flash to  make it run correctly  seems to be  popular fix for  guys  looking for a longer term fix.    replacing the cam gears/chain with  variable timing components  is about the same price,  but  there's a lot of people complaining the new parts just don't last.   

If the  body wasn't about to  fall off the frame,   I'd probably sink the dough into it.   
At this time,  the  level of degradation of the timing components is:  
  Reasonably quiet on cold start,  but noise  progressively gets louder as it warms up. 
 
When it starts sounding  like a  12v cummins,    I'm told to  not stray far from home.