see the different angle of the latch in the hood? (its pretty slight ,but its there)the unpainted one is more angled than the painted one....Jeremys is the same as your painted one looks like....thats your problem.... maybe you can cut it out and replace...when I bought my 400 hood , one end was loose on that latch and I spotwelded it in place after I put a screw thru it to hold it, so I know that piece actually is loose ,but might be spotwelded in place...not sure how hard to get it out, but its possible...( I dont have a picture of mine ,but can take if you want)
otherwise replace the other part for a 67 version...but later models 68 and 69 are better because they have the safety catch...

My friend Andy in town has a 67 , bought a later hood , and his mechanic filed down something (most likely the safety catch)to make it work, he has not had any problems driving w/o safety catch (as 67 s dont)...that is another route