Ok so , villain is the typical old (age 50-55) live regular. plays very loose and calls ALOT in all streets. The thing that makes him different is that he is bluffing alot. 

So hand goes like this : 

Nit who has missed bb+sb sits back in and posts 30. SB in the hand is a big spot and BB is villain , so i decide to upen AK47 (a high suit) UTG for 100.

its AK47 after all 

Sb calls BB calls (330) 

Flop : 6s5h3c , both check i bet 250  SB Folds BB calls

Turn : Kh (i dont have a fd) , BB checks i bet 750 , BB SNAPS

River : 7d BB tanks takes a stack of 100's then puts it back and throws 3 yellow chips in the pot (yellow chips = 500e) , Hero ?? 

How good of a card is the 7 otr for me to hero call ?

What rivers would you be likely to hero call generally ?