Both plants. Not everyone with them has registered yet though, it would be nice to nail down an approximate date range for when they were in use.

If anyone who has not done so yet wants to register their A66 car, please note on the form if it originally had the flat hood, the J54 hood with the decals or the J54 hood with the emblems?

http://www.hamtramck-historical.com/register.shtml

With enough input these things can be figured out.