Taking 12th street North out of Clarinda (becomes J20) Follow this around a couple of nice curves near Hepburn. Take a Left on to 71 North, continuing until you take a right on 92 East.
When you reach the town of Greenfield there is a nice new Casey's store (I do not believe it has 91 Octane fuel) at the 92 and 25 intersection. from there you are about 11 miles south of the freedom rock following 25 North. this road is straight but has some hills, and also just passes by an Iowa Aviation Museum.
There are a couple of small towns that your speed will slow from 55 down to a low of 25, but 92 is a pretty good road with good scenery and lots of giant white windmills to look at along the way.
The only place the road is not that great is along 25 North coming out of Greenfield. but it is without anything major (pot holes, ect.) and has decent shoulders along the route. There are also some curves, hills, and some trees close to the road, as well as lots of farm land.
There is a County historic Museum, and an Aviation Museum along 92 and 25. Once in Greenfield there is a Casey's and also a resturant on the square that is quite good