i found a nice 65 caddy project for sale. but there are a few problems. #1 the car is out of the CA dmv system. #2 the car is missing the vin number plate near the door (car has been stripped down for re painting) the seller has an old pink slip for it. the vin number on the pink matches the vin on the chassis. i also ran the vin number at the police and they said it was not stolen. will it be an issue that it is missing the vin tag near the door? like i said the vin is also on the chassis. and i think there is also one on the engine. any help would be great.
You may want to check with the DMV, but I doubt it would be a problem since their is a VIN somewhere on the vehicle.
You could make the purchase contingent on a clean title transfer. Sorry you have to do it in CA, though. 
VINs were not really standardized until the 70’s. I would have the seller do all the work as this is a huge PITA to do. There is also always the possibility that someone, who has an older receipt, can claim the vehicle. You need clear transfer of ownership throughout the years to be safe with your time and money.
It varies quite a lot by state, but you’ll probably need to get a “bonded title” where you take out a bond for the value of the vehicle. Although usually if it’s a total basket case project car, they may determine the value of the car is $100 or some other low number that makes the process easier. (Although that would be a major bummer if you fixed it all up and then someone with the original title shows up.)
Like electronbee says, VINs weren’t standardized back then. Usually the old serial numbers are just fine for title purposes, but I’ve heard of some situations where older cars that have title problems actually need to have a new VIN number issued to them by the highway patrol.
Does this mean that the California DMV no longer has the car on record in its system? Are you going to license it again in California?
I pulled an old oval window VW bug out of a briar patch that was last registered in CA. I did find an old registration in the glove box and I had a bill of sale from the guy I bought it from. I sent a copy of the old registration to Calif. DMV inquireing about how to get a lost title, and they sent back a letter saying something to the effect that they no longer had records for the car and had no real interest in the thing. With that letter, and the bill of sale I got the car licensed and registered in Oregon.
I don’t know how far back the practice goes, but modern cars have the VIN or partial VINs stamped in various hidden locations not well known outside of law enforcement. This is how the police can identify a car that someone has swapped VIN plates on or has been chopped. Your Caddy may have a couple that would help you confirm the identity.
You probably should go here and sign up to talk to these guys. Classic Cadillac Community.
Where in CA? Feel free to PM me, I have a customer who provides some kind of DMV VIN authentication service for just this type of situation. He is somehow licensed/certified by DMV to provide this.
There are services which provide national VIN searches:
https://www.google.com/search?q=vin+search