Having scrapped or saved many 351C engines I can say that the heat shield is not one of Fords better ideas.
Every 351C that managed to keep its factory heat shield that I encountered had a cracked exhaust manifold on that side.
All cracked at the same location - rear of the manifold just past the last port right where the heat shield stops.
I would not use them on a car that will be driven much - show car would be OK - but you are going to be risking your manifold and from recent experience they are getting harder to find.
I wish I still had all of the 4V manifolds that I have tossed out over the years.
- Paul