Do you still have the old dash? Classic Roadsters TDs were not exactly like others. Your best bet may be to have a wood dash cut to fit. The general shape is easy to trace from the fiberglass cowl. The mating edge on the reverse side needs to be routed out to fit the lip of the fiberglass cowl.
You might try contacting Class Roadsters directly. But they no longer make the Duchess and will probably tell you they have no way to help you.
Classic Roadsters II
39342 County Rd. 185, Dept. KC
Sauk Centre, MN 56378
(888) 722-6272
http://www.classicroadsters.com/
Paul Mossberg
Former Owner of a 1981 Classic Roadsters Ltd. Duchess (VW)
2005 Intermeccanica Roadster
If you own a TDr and are not in the Registry, please go to https://tdreplica.com/forums/topic/mg-td-replica-registry/ and register (you need to copy and paste the link)