I have read other 460 accounts than this one link, with more detail on what is needed. But the search function here does not recognize three letter words like 460 so it makes for a tough search! Try retitling your post to something less generic than "Motor Mount Question" and maybe someone will respond.
If your 66 currently has an FE engine, then there are a number of posts on here from me and others on how to modify the FE motor mounts to work on a 429/460 block. Others have purchased used Thunderbird 429/460 mounts from a parts yard and made them work.
I have also heard that the Crites mounts cause the engine to sit high and there are hood clearance issues. If you look hard enough, this has been a well documented engine swap on this forum.
Good luck with your swap, the 460 stock will be an improvement over a stock FE.