Smallblock efficiency or How to have your cake and eat it too

Could the OP explain the benefits of his short block selection versus starting with a 5.9 Magnum (or a bored to similar size 5.2)?

I used a "G-Tech" accelerometer to analyze a country road 1/8 mile pass in my 2000 Dakota R/T (stock with 3.92 gear, except cat back duals and a K&N filter system, 4200 pounds with me in it).

The HP used for that balls to the wall run according to the device was "78"
based on that I'm not sure 80HP is required to keep a 3200# A body up with traffic.

With the factory 46RE O/D, that truck gets 17-18 on the highway, and about 13 average in mixed driving, mostly city and semi-rural. At 50 MPH it gets 23.
When it was my daily, it got 14.2 average.