I started a thread not too long ago about Ram gear ratios. Lots of good info.
I'm towing a 12,500#GVW 5th and the 3.42 works well. I occasionally lock out 6th gear in hills.
In your case I would consider 3.73 even if you have to lock out 6th occasionally. I would also get the air rear suspension to help if you end up nose high.
Definitely get the Aisin.
I got the bucket seats and wish I hadn't. On long drives I would like to put a foot on the transmission hump and stretch a bit. Next truck will be the 40/20/40 seats.