I have not been to the LBJ library, but in 1992 the Henry Ford Museum in Dearborn had a Lincoln Continental on display that they claimed was the "assassination car". Could be that the one in the LBJ museum was the one that LBJ himself was riding in, or maybe it's just like the number of "Hitler's cars" or "Bonnie and Clyde cars" that used to pop up.
BTW, as a 5 year old kid, I lived about 12 miles from the scene of the B & C ambush, saw them whiz by our house a day or two earlier, and I was also on Lemmon Avenue in Dallas watching the JFK procession just leaving Love Field. Whatever that's worth.
Worth a lot..you were present where history was in the making.
Maybe the assassination car goes on tour? I don't know the explanation.
I was at a San Antonio bookstore when i noticed a curious photo hanging on the wall. It showed JFK in the backseat of a limousine just like the Dallas pics but it wasn't quite right. Then I noticed that LBJ was sitting in the back with the Kennedys! The proprietor explained that the pic was taken outside his shop on Nov 21 1963! I guess LBJ waited a day to make sure he wasn't shot like Connally was! LOL