Supposing you're not into faithful restorations...

There's really no point in replacing the connector housing unless you later intend to do a plug'n'play engine harness replacement with a new harness -- you'd like to just plug it in.

If you have the skills to splice or reterminate the rotten wiring, you have what's necessary to splice directly to the firewall side of the loom at the connector. Easiest method is insulated butt splices; more fastidious folks will use uninsulated butt connectors supplemented with solder and shrink sleeving. Throw away that gray connector.