1971 Slant 6 Vin Location

If your only criteria for staying with the slant is a matching VIN tag you might as pull the slant now and put in the small block. These cars really don't have much value regardless of original slant or replacement engine. When most people see a slant they think how it is a waste of a good car to have an underpowered turd like a slant six powering it. I personally would prefer a slant over any small block in an A-body regardless of whether or not the engine is original. I would consider dropping a slant into my 66 273 dart if the 273 ever goes kaput. I love the working room you get with a slant.

But to answer your question I could be wrong but I believe the VIN is stamped into the head gasket deck on a data plate. It is on the low side of the deck surface and it will be covered in grime they always are. If you look at the engine in this link you can see data plate in question at the head seam below plug #6.

http://www.forabodiesonly.com/mopar/showthread.php?t=208738