Don't worry about the RPM's.
I had an '01 'Burb 2500 8.1L 4.10 pulling a 6400lb trailer and climbing steep hills it needed to be in at least 3rd and I'd drop it to 2nd at about 4200RPM if need be....not very often.
Every time it dropped to 2nd and the 4200RPM kicked in my wife would hold on for dear life thinking the thing was going to explode
It took quite a few, "Dear, it's designed to do that," for her to slightly relax.
So, don't be afraid of the RPMs, just watch your tranny temp and let her rev.
BTW, I could 'feel it' behind me.
Me, DW, 3 sons (19, 16, 15) & RIP Joey the mutt
'11 Salem 26TBUD
'01 F350 RWD V10