What do you guys think about this?

Sunday morning a guy knocks on my front door. I get up, go to the door and see the guy step off the porch, and head to the gate to enter the back yard on the side of the house, away from the street. I go out and he tells me he is looking for a car he saw advertised on Craig's list, and the phone he called earlier about it is going to voice mail. We are near the end of the block, and he claims he thinks the address is 57XX, my address is 56XX. I tell him it would be around the corner, but doubt the address exists. Further, no one on the street has a Lincoln like the one he described, maybe it is a block over. I have never seen the guy, the gal with him or the car they were driving before. My dog did not like the looks of him.

Yesterday, dog is barking at something around 10:00, which is fairly unusual. My wife goes out front, sees what she thinks is the same car, with a guy riding shotgun this time. She asked me if the car did not have a grill, which it did not, so it appears it actually was the same car, and the guy driving it looks the same too.

This strikes me as guys scouting houses to rob. Of course, it is not illegal to be lost, or driving down a street knowing it is not where the "car you are interested in buying" is located. But it struck me as a bit off. I am not too concerned about it for myself, as the dog is fairly large, with a low tolerance for sketchy characters, the wife is from Texas and is a fine shot. I am debating whether I ought to call the Sheriff's department. What do you guys think?

Car looked just like this

That sounds sketchy to me.

I'd notify the police, install a motion light, and cameras in a couple of places.

what he said ^

Re-watch Home Alone. Use ideas to increase level of home defense.

Call the cops, it's Recon.

Perhaps the cops already know and just need one more call to shake things up....

I've been that guy before. Some Craigslist sellers are incredibly bad at telling you where the car is. The better the deal, the more time I'll put into trying to find it.

Call the cops. Craigslist or not trespassing is illegal

I think it was a scouting mission or a version of the "fake delivery" scam/robbery.

Scouting:
Once he had your attention he drew you out of the house. I would bet that is when guy #2 (who you did not see at the time) was scouting/casing the place.

Fake Delivery:
A nondescript van backs into your driveway close to the garage door. A guy with a clipboard approaches the door and rings the bell and knocks very hard to get the attention of anyone who might be home.
If you are home "the delivery guy" will say he has a delivery for address 55xx but your house is 56xx and he leaves.
If no one does come to the door then it is obvious that no one is home. From here the house will be broken into and the garage door will go up to load your goods into the waiting van.

I would call the cops and share your suspicion. Your ability to ID the two could be helpful and help to corroborate the knowledge of other victims. You are likely not the only ones this pair have hit with this routine.

Call th cops. They won't mind.

+1 for calling the cops. Worst case, they find nothing. Best case, you don't get robbed.

Oh, I am not getting robbed. Might have to mop up the mess afterward, if they actually got in the house.

Online report done, will e mail them the pic when they send the confirmation that the report is done.

From now on, suspicious travelers will be greeted with, "No, this address is XXX, but I'd be more careful how you knock on doors around here. Most people are armed and slightly paranoid."

This "fake delivery" is my biggest concern at my house. I sit very far off the road and the addresses are somewhat confusing.

If you think you might be witnessing a fake delivery happening try to get a picture and a plate number.

+1 for getting a pic of their plate. Honestly lost won't care, thieves casing the place will know they have been identified and know to stay away from the area.

I was fairly surreptitious in taking the photo; they did come back the next day in the same, distinctively ratty, crystal meth edition Crown Vic. That is a pic of the car in the OP

Toebra wrote: I was fairly surreptitious in taking the photo

Don't be "surreptitious". Make sure they see you taking the picture. That's advice from some of my LEO friends.