Last week the DOT showed off its proposals for a western bypass of Oskaloosa for US 63. There are four permutations, based on the locations of the start and end points of the bypass.
The south end would be either in direct line with gravel Jewell Avenue, or come at a slight angle from County Road G43. This is about where the IA 163 bypass of Oskaloosa from the old two-lane (former IA 432) begins. In either case, it is clear that US 63 is the subordinate route, and the overall distance will be longer than going through Oskaloosa.
The north end would be either by the Oskaloosa waterworks or farther to the north. The key difference is that the former does not include a new bridge over the Skunk River, but leaves intact a pair of slight curves of the road at and just north of where the bypass would meet present 63.
In either case, the bypass would meet the present road north of the railroad tracks, where a whole new overpass was recently built. If you look at the PDF maps (Option 1/2, Option 4/5), you can see a very old alignment for 63 just below (and beneath) the 63 and G39 shields.