Swapping a 65 273 with a Later 318. What's gotta Change?

The 273 is out of my 65 Dart. Ready to install the 318 (I think it's a 69). I have the adaptor for the crank and the newer radiator. Is there anything else I'll need to change? I remember one member here telling me I'd need to use the newer flex plate with my older 904. But both flex plates are identical. I need to figure it out by Monday. Thanks