[Gunner]

There is also no real way to register a specially constructed vehicle except under the SB-100 smog exemption. You may have run into information about "year of engine" registration, but these loopholes have largely expired. The vehicle will be judged as the year of build, and will have to meet smog regs for that year (sometimes the referees are kind in assigning an equivalent vehicle that is easy to match). But you will have to have 2005 or 2007 or whatever year the vehicle was built smog gear if you don't have an exemption.

I can see it being a very valid approach, especially with the donor-type cars like the FFR, to take a fully smogged driveline from a Mustang and transplant it intact.