Yeah it's definitely a big job. You need to change a lot of things
Parts wise you'll need new fenders, hood, bumper, radiator support, grill, valance, all front trim, light surrounds etc - everything you see on the exterior is different - and that's just the front end.
It'd get very expensive, quickly.
If you want a '67, don't buy a '68. I know it shares the same profile, but it's different enough to know it. It'll eat at you and you'll never be happy. Wait for a '67.
Ask Michael Pick here (the guy that has Hunter. there's a thread here somewhere). He has about half a dozen '67s in his yard.