Old School vs. New School Differential Gearing

[robbie_d68]

So, I have a question as far as Rear Differential Gearing.

Background: I currently have a 1972 C10, 350 SBC (1992 crate engine), 700r4 Auto Trans (1992), 3.73 gears (we think), long wheel base.

I have a 2007 Ford Edge with a V6. I have a quicker take off speed with my ford edge and I have a lower/smoother cruising RPM with my ford edge.

Question: how can a smaller engine, run smoother at higher speeds (80-90 MPH) than a bigger engine? I know there is a lot of discussion on here regarding rear differential gearing, so why is the current gearing ratios on vehicles today are so much better than the older models? I can run all day long in my Ford V6 at 80-90 MPH, but at 80-90 MPH in my C10, I am worried about messing something up. I do not have a tachometer on my truck, I am just going by sound.

Any advise would be greatly appreciated. I am looking at my next purchase to be gearing if I decide to change it.