STRONGLY suggest that you do not use US 6 east of Spanish Fork, Utah.
This road has high traffic, high speeds, blind curves, and heavy truck traffic.
It is considered one of the most dangerous roads in Utah.
In addition, there is almost always construction going on - plus poor shoulders in many places.
There is a scenic, low-traffic option that does involve more climbing.
From Delta take Hwy 132 to Nephi and Moroni. (Mod traffic east of Nephi)
Take Hwy 116 to Mount Pleasant, then US 89 north to Fairview.
Hwy 31 climbs the Wasatch Front, then Hwy 264 goes to Scofield.
(Very scenic, high country area)
Hwy 96 takes you to US 6 at Colton.
There is a seasonal store in Scofield and a historic general store at Colton.
Plus, there is a cutoff road between Colton and US 191 - Emma Park/Kyune Rd.
Also, there are nice back roads between Duquesne, Vernal, and Dinosaur.