I am sure it must be the same bike.
There are a lot of things on it I would do differently. First is the fugly exhaust. I have found several used mufflers from an R80ST or G/S that would work in the correct location. Just a matter of building a set of headers from the heads to it.
Also the Bultaco tank has got to go. The R65, R65G/S, R80RT all use the same tank. Why change it.
I don't have a problem with the Yamaha YZ forks. They work good, are relatively inexpensive and the 21" front wheel is a lot cheaper than a BMW G/S front wheel.
All the other "stuff", fenders, skid plates, etc are available as aftermarket repops. It all depends on the budget.