The preferred place for the radiator is on the cool or spark plug side of
the engine. The water pump inlets and out lets are on the hot side
complicating the plumbing.  I suggest cutting off the top of the RX8
front cover and that includes the alternator mount and welding
in a 1.5 inch  OD 90 degree tube bend. The top mounted
alternator won't fit under a lot of cowls anyway.

This works for the 13B water pump as well.

This will cut about 18 inches of pipe or hose out of the water plumbing.

If the rad is under the engine use a 180 degree bend to go straight down.

Paul Lamar