I rode part of this route, Evanston to Michigan City, en route to South Bend, way back in 1991! I can't believe it's been that long.
(I had a black and orange Cannondale mountain bike - I could have purchased a Bridgestone and I have no idea why I didn't. I thought Cannondales were so cool when I was 20.)
Were I to undertake this ride today, I'd just use the google map route for bicycle. I just reviewed the suggested route. It's not awful. And there's some nice parts, like the ride through Indiana Dunes.
The most direct route would be through Gary, which I think is probably undesirable. I still remember my ride through Gary - I had no maps. I went through Gary because I was navigating by following the lake. There were four ferocious junkyard dogs that came barreling at me from various directions as I made my way through town. For those terrifying moments, I became a very strong rider.