A904 for 360 Magnum

Depends on the year of your 904.
Pre '68s had a different convertor snout (and thus crank flange pocket) size, and the input spline count and diameter also changed.
If the 904 is original to your '67, you will need an adapter bushing for your Magnum's crank hub in order to properly fit the torque convertor. The other option is a custom built convertor.
If your trans is '68 or later, you should be good to go.