I followed Sammy's instructions to the letter, printed out chapters 2 and 4 of the TxDMV Assembled and Rebuilt Vehicle Manual and highlighted every pertinent line and paragraph. Took it all to the Ellis county tax office in Waxahachie. Explained to the clerk what we were about to do: She called over her supervisor, who brought out the same TxDMV manual. We went through each page and step together, they reviewed all my documents, the clerk keyed it into their computer. I only had to reminder her to add "REPLICA: 1965 FORD" in the remarks section.
I paid a total of $139.50: $99.50 for registration and title app, and $40 for personalized custom vehicle plates. I paid NO sales tax. I think the key is having "ASSEMBLED" as the seller on the application.
Yesterday I received my Texas Certificate of Texas from TxDMV ...! Woop! Just waiting on the license plate in the mail now.