Moving the engine farther back by adding a bracket will cause the stern to lay deeper in the water. Besides, I am not sure that you need a kicker with that engine. It looks like that engine can go slow enough for trolling. A good splashbox will keep the water out and removing a kicker that you do not need will make the stern loose about 120 pounds and raise the stern a bit. Looking at the pictures it seems to me that it used to have a splashbox with a drainhole on each side of the engine and if you want to keep the kicker you can probably install it on the medium raised part of the transom,maybe cut it out just a bit wider, and that way you do not need a kicker bracket.
A splashbox would be what I suggest.