My 360 Engine is running reverse once turn off.

When you shut it off and the piston is coming up the bore it has a charge of fuel & if the idle is set too high it will also have a good charge of fresh air if the head is too hot it will combust without the need of a spark as there is not enough momentum to carry it through forward rotation the piston is forced back down the bore in reverse.
Have seen this on new engines without carbon buildup .If my engine is extremely hot enough to cause preignition i leave the auto in drive with my foot on the brake at idle then turn the key off it causes the engine to lose rotation more rapidly