Help Required: Slant 6 Engine Identification

I'm in Australia, we are restoring a 1964 Dodge Dart GT, but with a few tasteful period modifications. It's a nice car, it's coming along nicely, (photo included) but I'm pretty sure the engine is not the original. In Australia, we recognise the 3-welch plug engines as 145hp and 5-welch plug engines as 160hp. All our engines have the oil filter remotely fitted to the manifold side, with pipes connecting to the oil pump. The engine in this car has 5-welch plugs, the oil filter is fitted directly to the oil pump behind the distributor. Pretty sure it has been reconditioned recently, goes great, no smoke, starts easy, behaves itself. Can someone identify what this engine is originally out of? Engine number is: PF225R-24540814.

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no help, but, nice looking car!