I don't know about 68 but the 67's are smaller and a little different dimensionally than the 66's so I can't imagine them making 68's the same again..
Like you say, tie rods, draglink(?) and other associated pieces.
68-69 spindles bolt up without a problem and the tie rod taper is the same size. To use 70-73 spindles you will need the different tie rods. There is a nice write up in the faqs detailing everything you will need for the swap.