Finding My Boss's CSX

[LMH]

Hey all
This IS LONG, so bare with me...
Shortly after I started my job a few years ago, my boss told me he owned a 289 Cobra back in the day. He was the second owner and traded a brand new station wagon for the Cobra. Apparently, the original owner had a baby on the way and the Cobra didn't fit into the picture.
I have been trying to find out what his chassis number was and where the car is today. (thanks for the help so far Ron!) There is a somewhat interesting story that goes along with the car but I would just like to find where it is today.

Here's the problem so far... Bill (my boss) doesn't have the memory he used to. (neither do I for that matter) He has no paperwork on the car and doesn't know the CSX number. He did not ever register the car with SAAC or the registry, so his name is not listed as a previous owner. He didn't remember the original owners name or the guy he "sold" it to either. He remembers selling the car around 72 or 73ish. He owned a new Pantera at the time also.
Ron checked the current registry for me but Bills name wasn't in there. I thought I'd hit a dead end.

A few weeks ago, a local AZ Cobra member, nicest man in the world AND alumninum (yes, I said aluminum) SPF owner, loaned me a bunch of his old records from when he owned CSX2335 ( thank you Gerry). Among the very cool stuff was an owners registry from 1976. I looked through it and found a car that was in Tucson in 1976 with a previous owner also having been in Tucson. I showed Bill the registry and the previous owner's name, we'll call him Mr. X, and with jogged memory says "that's the guy I sold the to!". He is sure that Mr. X is the guy he sold the Cobra to.
I thought I had found Bills chassis number.
The next problem then arose that Bills car was green with black interior and a search on that chassis number showed the car originally being white with red interior. Bill remembers buying the car around 1967-68 and I doubt it had both the interior and paint color changed in that short time frame. I may or may not have found Bills Cobra.

So I'm at a seemingly dead end again. I have been told that AZ does not keep old registration records, so I think that's a dead end.
Anyone have any other suggestions how to find Bill's original car?
Larry