The differences could fill pages. Approximately nothing is the same on the two motors except the displacement & block weight. 351C heads will fit on a 351W with some fiddling but other parts are necessary to make it work. The W has better oiling and slightly thicker cylinder walls, and is still being built while Cleveland stuff is getting very hard to locate. The Pantera bellhousing & motor mounts fit the W. This is not really a bolt-in swap unless you are well equipped & experienced, and not in a hurry.
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