Wait, you mean the other way around? Manchester to Delaware was 4 lane first. Delaware to Dubuque went to 4 lanes in 86 ish?
Independence to Delaware was late '70's. I worked on a repaving setup for DOT on Hwy 20 outside Farley while in college (early '70s) so that section was there long enough to get resurfaced. Lot's of fun (not) driving 2x2 "hubs" with a sledgehammer into gravel shoulder to set up a string line for the paving machine.