Speeds vs Gear RAtios

[Olde Bob]

I am a long time Rammer, having bought my first one in May 1994, (still gotter' @ 534,890 mi) but have a question about gearing on the new '16 model 3500, 6.7 with the Aisin. I am torn between the 3:54 and the 3:73 diff. What RPM"s should I see @ 70 MPH in 6th gear with either ratio ? Anyone ?.. Thanks in advance..:-

Olde Bob