Too cold. The factory used N13y Champions. Autolite says their 65 or 66 is the same plug. Use Champions that the engine came with. If you modify the engine then you can mess with heat ranges.
The guy that built my 360 (Bob Lambeck) installed n65y plugs but they caused noise in my stereo system being non resistor.
They cross over to autolite 62 and 63. Couldnt get 62's so i went with the 63's