99 F450 7.3 2WD Standard Chasis Cab FB

Since I'm not exactly sure what was there in the first place I'm hoping someone can confirm the part I'm going to replace.

Loud screeching battery lights, then nothing... belt was a little loose and is rubbing over a metal piece instead of the pully what used to be there.

Anyways, I BELIEVE I'm looking for the dual idler pulley assembly.. or
Should I just replace the one pully? and if so which one is it?
I assume its the smooth one but anybody have a PNs?

Hopefully, the pics attached work

 

That is the tensioner assembly. Has the tensioner and an idler pulley all in one. Replace as an assembly. And get a new belt while your at it.

 

Yeah I need to order a new belt... Gator belt?

 

I have had a gator back belt on my F150 for 3 years now. Has been fantastic. Can't say how they are on the 7.3 as I have a Motorcraft one on it.