You'll need a 360 flexplate like what B&M makes... 10236 (727) or 10239 (904) come to mind. The b&m flexplate balances the assembly to use a neutral balance converter like on the 318. It has a half-moon cut out of the flexplate.
The converter will work, will likely stall a bit higher do to extra torque a 360 generally makes. If you liked the way it acted with the 318, you'll likely be OK with the 360. Unless you are changing from a 727 to 904 or vise-versa, no problem using what you have.
