I think IN 46 between I-69 in Bloomington and I-74 in Greensburg need an upgrade more than US 50 in Indiana, possibly even further west to Terre Haute.
I last drove IN 46 from TH to Bloomington in the Before Times, but I definitely noticed an increase in truck traffic. The hills around Spencer desperately need more climbing lanes in addition to the old old one near McCormick's Creek -- not just to get around trucks, but all the locals driving their 1959 Ramblers at 32mph.

The alignment through the hills just isn't very good, mostly the original lines. But I agree: Getting any meaningful improvements in the rural areas seems next to impossible now. (Ellettsville to Bloomington is nice now, but that mostly serves commuters.)