Difference in Hiway RPM-3.73 to 3.42

[custom10nut]

I’m wondering what the difference in in Highway RPM would be if I was to change my Rear End gear from 3.73 (factory peg leg) to 3.42 (new Yukon Posi unit).
Currently, it runs well over 3000rpm at 65-70
My ultimate goal is to get a lower Highway cruising RPM, when I change to the Posi unit.
Many will say “just put a 700r trans in”, but I don’t want to do that.
I’m just wondering how much difference there is between to two ratios.
I’m not expecting “Better Gas Mileage”, but just want to lower the RPM to go easier on the engine revs.
I know the change to 3.42 won’t make a HUGE difference, but I think if I went to a 3.23 it would affect the performance (I.E. Turn it into a Toad)
Thanks in advance