Hi Barry,
I just grabbed those numbers late night from one chart. Since you don't know of any Hamtramck 1970 Darts I did a little more checking. Total 1970 Dart production was 191,986 but almost all Darts built for sale in US were built in Canada. In review, I think the Ward's chart is wrong for Dart Hamtramck production. The Valiant, Barracuda, and Challenger numbers all seem to confirm:
Hamtramck Valiant 233,157 plus LA Valiant 8,400 for total of 241,557 US
Hamtramck Barracuda 45,788 plus LA Barracuda 9,711 for total of 55,499 US
Hamtramck Challenger 67,126 plus LA Challenger 15,906 for a total of 83,032 US
These three would give a Hamtramck production total of 346,071, which is close to your high number recorded. Seem right to you?
Ty