ok i'm a R/T guy obvously, when i look at it a regular cab rt is faster than a club cab rt. Same engine weight is the factor, the durango has more weight but more ponies, the 4.7 reg cab is lighter but less ponies. Lighter is better in my instincts. I've seen so many flames between the 4.7 guys and the R/T guys and to be frankly honest with you they are both good engines and are equal in my eyes. A 5.9 R/T reg cab is just as fast or a little faster then the 4.7. The reason the 4.7 is aluminum, less weight.
I hate to say it man but i'm going to say the 4.7 is going to edge you out, but i would race him anyways. A good race is always fun. Just be cool about it and chat afterwards and compliment each other on the others car. I've been smoked so many times by guys who were pricks before i raced them then when i was done i went and talked to them and complimented them on their car/truck and they ended up bein nice guys and tellin me that they were supprised at how good my truck ran for a truck. They expected worse.