360 to 904 trans ( in a 318 car)

Yup, as stated above, just use the B&M 10239 flexplate.
The motor mount brackets will need a spacer between the driver's side rear engine ear and the bracket on the 360, otherwise the 318 mounts will fit fine.
Depending on what your 360 came out of; you may need a 360 passenger car oil pan, pickup, and dipstick. The 318 pan will not work on the 360.