leave body side molding or remove it?

just had the same issue with a 69 swinger 340 stripe delete car. The previous owner swore up and down that the side molding was factory. it was the ugly squared off metal trim with the plastic insert. I looked for any indication or proof that he was correct and founnd none, so decided to go with the stripe. I origionally planned on filling the holes myself, but being a novice, and realizing the damage i could have done with the welder, i paid a ton and had a pro do it.

FWIW, The type moulding you are describing is aftermarket. A lot of dealers put it on both new and used cars back then. I probably put a few hundred feet of it on myself. It was universal. The aluminum part came in long pieces you cut to fit each panel, allowing for the metal end caps. You attached it with small screws or pop rivets. The vinyl insert came in 50' rolls and various colors.
I also installed alot of aftermarket vinyl tops. The trim for them was universal also and we had a special 'bending board' to custom fit the trim.

To the OP, I've seen cars I like with the trim and I've seen some that would have looked better without it. Mostly depends on the condition of the trim. If it's nice it looks good, if it's getting tired you need to get rid of it.
Dallas