Ben,
Having been there and done that, I can assure you that you don't want to bring the car in with the motor and trans in it. It comes as a chassis, and motor parts. If you have the motor and trans in, you have to meet all the safety and emission standard for the YEAR OF MANUFACTURE. Or you can declare it a racecar, which limits you to off road events, and you have to let them know when the car will be exported out of the country.
Now you see why the replica manufacturers do it the way they do. As to titling your car, you will have to check with your local dept. of motor vehicles. It can be as simple as in Ga.(if you know how to do it) as presenting a bill of sale for a 1966 Ford GT. Once you have the tag reciept, it can be retitled if you want. AND it doesn't have to meet any of the emission requirements as there weren't any for '66. Other states have strict requirements. You just have to check and see. If you know someone in the local police dept., they can be a load of help, especially if they are a hotrodder.
One of the declarations you will need to fill out describes most of what we have been talking about. Here is a copy of the one I had to fill out. I blew up the pertinant parts for easier viewing. I hope it comes through OK.
As you can see, most of what you have to chose from really doesn't apply. You have to make a best guess. This is mosty for taxation than anything else. Check with more than one importer, as they each have their own way of accomplishing the same thing.
If you need more info, contact me. I might be able to save you some time and money. I wrote an article some time ago about buying and paying for a used or unfinished kit. If you would like a copy, I have it stored on my computer and can forward it to you or anyone interested. Some of the info could be updated, but it sends you on the right tract.
Bill