In case you are wavering on using the cork in the kits or silicone, as supplied, the cork is either too thick or too dry.
When you see how pliable and compressible the cork is supposed to be v. how you get it, you can begin to understand the issue.
You need to compress that 1/4" thick cork down to less then 1/8".
Ford ALUMINUM intake manifolds do have the WELL DESERVED reputation of being fragile on the outermost bolt flanges OFTEN breaking them completely off while attempting to tighten down those bolts while using the cork gaskets.
True the factory used them with little issue but they were very soft and pliable under those conditions.
The black rubber ones sometimes supplied in Cleveland kits are more pliable but literally need to be glued in place before you set the manifold.
By far the simplest solution is to use the proper silicone.