Yes, this is an original AMT annual kit. And yes, I 'ruined' it by building it. I regret nothing... I think it looks way better like this than it did as a bunch of styrene lumps in a box!
It is mostly box stock, aside from the '25 T kit Lincoln valve covers, '65 Lincoln custom exhaust manifolds, the '66 Buick air cleaner, and the Hurst mags from a '66 Mercury kit. I also lowered it by drilling the axle holes higher in the chassis. Wonder if the tooling for this one still exists, in some form? (There are many identical parts with this and the '66 promo I have, but not a lot of similarity with the oft-reissued '65 kit...)