The 67 and 68 are actually the same kit, save the front grille.
That said, I have built the 67 and I ran into a couple tricky parts. First, its a real tight fit with the engine when it goes in under the body. The engine sits almost touching the forewall, and it took me fits to get it in.. I ended up having to remove the distributor, and glue it back on once the body, interior and chassis was all together.
I also recall having to build up the rear spring slightly so that the car did not drag in the tail.
Its not a kit that just falls together. This is the second one, which came out better than the first (which I don't have pictures of).
I actualy built 2...here is the Dana version I did thanks to Jason Rothbeb's donatin of parts :-)