I want to confirm that if I want a bike that has the original engine then the stamping on the engine and the number on the DTIF sticker on the frame need to be the same?
On my 73 175 they match and was assuming that is the same for 1971 bikes too?

Thanks for the help

My 1971 AT1C numbers match.  It has same VIN number on motor, on the sticker, and also physically stamped in the frame as well.  Hope that helps.

Generally speaking, yes, matching numbers when they left the factory.

A handful of bikes might have numbers where they are close to each other, but this is very rare (this is anecdotal, so might be complete bollox! ). 

my 1971 DT1E engine and frame VINs (start with DT1F) match

As mention numbers will match if the engine was never exchanged. Don't forget there is a USA VIN table available on the site, just click Tech Library at the top, and the VIN table is one of the quick links.

Thanks guys I appreciate the replies.