904 in 65 Valiant Signet (US Dart)

You will have to find out the year the trans was built by cleaning up the drivers side pan rail & checking the trans ID number.
In '67 Chrysler changed the 904 input shaft from 19 to 27 splines. This resulted in a larger diameter input shaft & the reaction shaft inner diameter was increased to match.

You can decode your trans ID here.
[ame]http://www.mymopar.com/downloads/transguide.pdf[/ame]

Cheers. Gaz