Here is what I have...

NICE !!! My first 57 (SD Courier) also had a 1969 302. maybe not a very spectacular engine swap, but they make great drivers. I also have a 302 in my 34 2dr Sedan. These engines will go 3/4 to full throttle on the Autobahn all day long.
In a 57 Ford a SBF engine also makes a big difference in weight distribution. My Del Rio has a 351W and it takes a lot of weight off the front axle, compared to the Y. Certainly improves handling. That said, I still love my 292 in the CS. wouldn't want to have any other engine in there.

Thanks Lynn.  In my mind it's a 300 anyhow.  But the price seems too good.  He said it has a Cleveland 351.  And is not running. 

There are artist renderings of the Custom and the Custom 300 interiors in the "'57 Ford Custom and Custom 300" sales brochure. I will try to post pictures this afternoon. Not much, but it is accurate.

There are two Custom models. The base Custom has the exterior trim that the car in the ad has. The Custom 300  has the gold trim on the side (similar to the Fairlane 500) and an upgraded level of interior trim. I think the base Custom only offered the gray interior while the 300  could have had blue or green interior. There were some early 300s that had a single full length trim (no gold).

Exactly. Those you pictured are the ones that always come up when I look up 57 Fairlane hubcaps. Thanks for the info 

They appear in my Custom 300 dealer brochure as an available option, so I'd say they could be had on any 57.
Usually these are what you'll see:

I'm not supposed to use Facebook but dang!!!
But you know how it is.  Can be a scam.  Too far north for me to check it out.

Also some replayed with it not being a true 300. 
Can some mention what are the tells for a 300?

Can't seem to find the answer anywhere.

Are these correct for a 57 Fairlane 500 too? Or are these T bird hubcaps?

Seem to keep seeing a different style on Fairlanes.

Good. I'm not the only one.