My memory could be faded, but I remember the heads being the same as in George's photos (having both the verticle and horizontal bolt holes). So when you put on headers you could use either or all bolt holes. The exhaust manifolds look to be the correct ones (mine are all rusty). The passenger side exhaust manifold has a positively tiny diameter where the heat riser flipper is (when you consider it is behind a big block). The only minor diff I noticed is that our fuel pumps had the canister type of fuel filter as compared to the later style without filter on it. Don't know if all 67's came one way, or whether the fuel pump pictured is from a 68. There were minor diff's on
oil filler caps and things like that from the factory.
If it really makes a diff I could check tonight in the garage, as I believe the original heads are out there somewhere. The exhaust manifolds are also. If you are going for absolutely original, then you have no choice but to use the original (terrible) exhaust manifolds. If you are allowed to cheat a little, you can use the later 428CJ exhaust manifolds, which have to be worth at least 10 - 15 hp, and look nearly the same. It would require different H-pipes, etc. I do recall seeing them installed on a 67 mustang in years gone by, but I never did it myself, so I can not say for sure there would / would not be some minor issues which had to be overcome.
As to the comment that dual quads were hard to tune, I never really found that to be really true (assuming that they were the original type which were designed for the task). The factory jetting was fine (for NJ), maybe a tad rich on the primaries. The key was to end up with all the idle screws nearly the same after you were done fooling around.
Joe