if you're looking for numbers on a stock magnum cam you're unlikely to get it from mopar. if you can find the early '68 road runner advertisements they'll state 276/292 for cam duration seat timing. if you look at modern numbers they state 268/284. the stock cam has long closing ramps and the 268/284 doesn't include all the closing ramp. the 276/292 number does include ramps down to, or very close to .006" lift. i went thru this before and being an old school cam degreeing person stuff got real confusing trying to pin down a number with an asymmetrical lobe. as near as i could tell the 268/284 number is .006" lift on the opening side and .009" lift on the closing side. it gets even more confusing when trying to pick out a stock replacement cam from the second tier grinders who include all the ramp on their seat timing specs. the cam you have might be the 256/260 cam that was commonly used in non-magnum engines. the only problem with that is the lift numbers don't jive.