There is another way to get to I-74 from the Frankfort area that does not involve the under construction portion of IN-28, but instead uses very local farm-to-market kinds of roads for about 30 miles. From the Frankfort Municipal Airport take IN-28 west to the (very) small town of Jefferson and turn south onto S 450 West. At another (very) small town, Manson, turn right onto W Manson Colfax Road and continue straight on that to Colfax. Leaving Colfax, this will bear left and become 850 West Road and then N 1050 W, but you're only on 'both' of them for about a mile and a half before turning right onto W 900 N. Another five and a half miles and you'd turn left onto 700 East down to the town or Darlington Woods. Do a jog right (turn right, go a couple of blocks and then turn left) onto Madison St. and take that through town to IN-47. Make a right onto that and follow it into Crawfordsville and then US-231 onto I-74.
Now, while that may sound like a lot of navigating on tiny roads, but I'm sure that you're relatively familiar with them and at least some of the towns you'll be navigating between. And the standard speed limit on rural two-lane Indiana roads is 55 mph. So if IN-28 is still a no-go, then I would at least consider using such a 'back' way to get where I'm going.
AZBuck