nice looking car, but I honestly think its overpriced.
Technically if its registered as a 66 Ford that's a fraudulent registration (seach for posts by Morgester, there is an amnesty program being evaluated to correct these vehicles, but there are smog issues). Now you could probably get away with it, the question is for how long and what will be the consequence when it catches up.
All that aside, the chevy motor will kill the resale value on the car. If that's what your husband has his heart set on, great more power to him. Just understand that it will hurt the value, and many buyers will not want it.
Regardless life will be a whole lot simpler to find an existing vehicle that is registered under the SB100 program. There are a few here on clubcobra in the for sale section, just search on SB100. Not sure if this link will work but here is a search I did just a minute ago
http://www.clubcobra.com/classifieds/showcat.php?cat=2&stype=1&si=SB100&perpage=12&sort =1&stype=&limit=&cat=2&ppuser=
You can also check on Cobra Country
http://www.cobracountry.com/home2.html the ones with SB100 are easily identified