I went the 67-72 route with my 66, or at least tried to. I wouldn't waste my money on them, there is just too much modification required to make them work. I ended up making some from scratch and will be covering them with trim panels.
Dave 66 GMC- father /son project with the "GMC KID" 36 Chevy PU- 4x4 lifetime project 64 Skylark- wife says its hers