Sensor is located on the driver's side of the engine almost directly behind the head and down by where the transmission bolts to the engine block, just above that area. On the big block (I have one of those) it's very difficult to get to. I took mine to the dealer. From what I hear, the small block can be done at home but it's a lot of work and small hands are a must. Being that you have a big block, I'd suggest the dealer to the work. If when you tell them what to replace they look shocked like they have never had to replace one, take your AV to another dealer. The one I used knew exactly what I was talking about. Had my AV in and out in a few hours.
Good Luck