The Thunderjet was the std passenger car 429 from 68 to about 72. Nothing but a name really. The early 68-70 head castings had smaller chambers and screw in studs that set them apart from the later heads. These are good starting points for a perfomance build due to these two features.
Essentialy, the castings from 68-72, C8VE, C9VE and D0VE are the same, with minor engineering differences, the largest difference is the D0VE head could have smog holes drilled in them. In 73+ is the major change, when the chamber size increased to 97+ cc's, seats are deeper, valves are shorter and they started using the pedestal rockers. Porting these heads help, but it's nothing compared to a D0VE or earlier revision head.