Sorry if I'm happen to be beating an old dead rotten horse, but I can't seem to find the answer-

Can you change just the tensioner pulley or is it a non serviceable assembly? Because even the little ma&pa auto parts stores tell me I have to buy the whole assembly, but I don't really want to shell out $40 for a tensioner arm that still works just fine, it's just the pulley that has bearings goin out.

Looking through forums the info if any is all contradicting, too

 

Over time the spring becomes weak as will. The tensioner will bounce with the engine running. IMO I would change the assy.

 

You can get a grooved and flat pulley separately (for the 4.7) but as stated above, don't bother.
Steve

 

That makes sense but the reason I asked is because I got a wrecked 4.7 that had all new pulleys in it. I don't know if any of that would fit the 5.7, I presume the actually pulleys would. The tensioner arm seemed strong as anything and holds the belt well, just looked at saving some bucks wherever possible since that darn pulley ain't the only little irritating problem I need to fix.