The difference between the XE256 and XE268 is just 7ft.lbs. of torque and that 7ft.lbs. moved only 500rpms down.
And 500rpms less is like easing off the gas pedal about a 1/4". Am I missing something here ? What is it about the RR cam that you don't like for cross-country cruising and low speed stop and go. That's primarily all part-throttle driving. Any cam can do that and you won't feel the difference unless you really stab the gas pedal.
Maybe all you need is to swap the 3.23 gears for 2.94 .
Also, removing an RR cam out of an RR ? Why not just buy a land barge C-body instead. LOL