OP,
Do yourself a favor. Buy the right tool for the job.
For that much weight, it is a dually.
The 3.42 axle will tow it in 5th gear, with downshifts to 4th.
The 4.10 axle will tow it in 6th gear, with downshifts to 5th.
The SRW will be very close to maximum rear axle capacity and trailer tow rating. Do you want that?
The DRW will have extra capacity.
Don't forget to adjust the weight ratings for options (ratings are for a stripped truck), people, FW hitch, and anything that goes in the truck.
Measure twice, buy once.