Serpentine belt length - V8 5.0L

[SoNic67]

I wonder what is the right lenght for a serpentine belt and tensioner position on a V8 engine...
The belt that is suggested by Motorcraft is JK6-943-AA (93.4" ?)
The Advance Auto suggests Dayco 5060935 (93.5")
Amazon part finder suggests Goodyear 4060940 Gatorback (94.0"), Gates K060938 (93.8"), Prestone 935K6 (93.5") and same Dayco (93.5")...
So on and so forth.

 

[swetrid]

Any of those will work, the difference is minimal.

 

[SoNic67]

Do you know if my belt tensioner (pic above) is "in the range"? It has the three markings close and one further down. Is the further one for max travel when remove the belt? Or is just "belt needs replacement"? Why are three close toghether - between two are "normal range"?