I've switched out take-offs and not had an issue w/ headspace.
+1
If timing/indexing has to be right the cost goes up. Cut a partial thread and perhaps a finish reamer. Otherwise take off one barrel and install new. You'll need an action wrench if you're doing it yourself. Also get the wrench as close to the barrel as possible so as not to twist the action.
Going to a good smith is a better idea though.
