Is the number on the block the vin?

I just bought a 1969 Charger R/T. It does have a 440 under the hood but the previous owner (now 80 years young)said that the engine may have been swaped out back in the 70's. I need to know what numbers should match what and where. There is a guy out in Texas that has a 440 engine for sale that is date coded for 1969. Is this good enough to make my car a numbers matching car again if the original engine is missing?  

No, the VIN and the engine i.d. number are not the same. Year One used to have the engine number info on their web site. It is no longer there. Instead it says: "For more complete information on identifying Mopar engines, and a listing of Mopar engine codes and block casting numbers, call our toll-free tech support line for engine code info: 1-800-Year-One extension 172."  Maybe you could try that.
I do know that a '69 Charger R/T 440 should have a VIN that looks like this: XS29L9*******.  The "L" indicates that it has a 440 4-bbl engine.  

Thanks, Where is it located? The number after the "L" i'm guessing is the year?  

The VIN plate is riveted to the drivers side top of the dash board (visible thru the windshield). You're right, the 6th digit is the model year.  

Purchasing this engine dated 1969 will make it a period correct motor, but not a numbers matching.  The last digits of your VIN number should be stamped on the lower pad on the block on the passenger side of the motor.  Sometimes the whole vin number is there.  If there is no number, it could be a warranty block.  The casting date should also be on the side of the block, usually in big numbers.
You should have a number stamped on the rad support as well.  This is usually the last seven or so numbers of the vin.  Another place the number is stamped is under the rubber moulding on the trunk lip.  Lastly the tranny. If all these numbers are the same, you got yourself a numbers matching car.