Help Required: Slant 6 Engine Identification

Sorry Nigel, but I can't help you with engine ID, just wanted to say what a great looking Dart you have! My intro to the Dodge Dart was when my dad bought a new '64 back in the day! Still searching for a clean, cheap one myself. Bucket list item!
Keep looking, you'll find one. Mine came out of California about two years ago, it had been resprayed (acrylic) but it will do for a few years then I'll strip it down and do it properly. In the meantime its had a Valiant (Australian) disc brake conversion, front sway bar, new interior, window rubbers and so on. Just waiting for my carpet kit to arrive then it's ready for registration. Oh, and the transmission input shaft bush that Dan wrote about, better not forget that, HaHa!