should the engine number on block match some numbers on the Vin (1987 930)

no- the engine number is just that- the 5th number in the vin will tell you what KIND of engine you have- but no numbers from the engine will be found in the vin- if you want to know if that is the original engine, you should ask the person you bought it from- you didn't ask? that would be gamblin' with your money-

If you dont have a certificate from Porsche this might help out: http://www.porsche.com/usa/accessoriesandservices/porscheservice/ownerservices/certificateofauthenticity/

Also here is Porsche of North America's # 1-800-PORSCHE

If you call Porsche, they can tell you the details for free. It costs about $100 to get a COA from them, but may add a bit of value to your car, especially if you have matching numbers.

I have a 1981 911sc euro model. There is a number on the gas tank and engine block that matches the VIN.

James, most likely your block has been replaced by an unstamped factory case, which was then incorrectly stamped by someone who misunderstands the concept of 'matching numbers' in a Porsche.

If you want to verify vin number, use this tool: http://vin- location.com