Roadrunner or Not

Did they even build B bodies in windsor for the 68 model year? C bodies yes, A bodies, yes

68 -70 RR's were only built at Lynch Road (A), St. Louis (G) and LA (E)

RM23F8R245761

A car, built at a factory that didn't produce them, was special ordered with a 318... OK.

The VIN on that car is totally fabricated. If the trunk and radiator stampings match the vin, it's a fabricated vin number. It's a fabbed vin based on a B body coming from windsor alone!

Ding,Ding,Ding...we have a winner.

Someone got creative with a stamp kit and likely a fabricated/altered title from another state and got semi legit paperwork for a (possibly) stolen or (perhaps) rebuilt or salvaged car.

If the guy doing this had any brains then he should have used the 383 engine code (H) along with an actual B-body plant code (A,G,E) to avoid raising any more red flags then a car with no VIN tag already would.
Trying to pass off a car with no VIN tag as some sort of factory special build with a motor never offered from a plant that never built B-bodies is something a Chevy guy would do.