[DSYenko]

I have a few question on a 1971 Nova SS big block 4 speed car I located today. Owner says it's factory big block 402 car with factory 4 speed.Gold in color but original engine has been (REPLACED) with another 402.Has some rust but not bad.Black bench seat.A friend of mine went and took a quick look for me a said it had a 12 bolt rear.What do I need to be looking for??
Is there anything to look for in the vin or trim tag to verify it's a original SS big block car and what is approximate value needing restored but very fixable. Thanks guys in advance.