Kentucky and Ohio will get more than $1.63 billion in federal grants to help build a new Ohio River bridge near Cincinnati and improve the existing overloaded span there, a heavily used freight route linking the Midwest and the South, officials announced Thursday. Congestion at the Brent Spence Bridge on Interstates 75 and 71 has for years been a frustration for travelers, a bottleneck on a key shipping corridor and thus a symbol of the nation’s growing infrastructure needs. Officials say the bridge was built in the 1960s to carry around 80,000 vehicles a day but has seen double that traffic load on its narrow lanes, leading the Federal Highway Administration to declare it functionally obsolete.