Well, yours is going to be different also. I'll bet you've got a lot better quench/compression than the factory motors. Also, the cam for the 390hp motor is a lot better than the stock truck cam for turning RPMs. Also, the carbed intakes (if that's what you're using), are also more RPM capable than the truck intake.
I got my new throttle cable today, so tonight we'll see what it'll really do. I'll try to get a video if it actually runs.