You'll probably have to mod the dust cap so check out this thread:
Coaster Brake Dust Cap Mod
You'll also have to bend the brake arm a bit. There are instructions for that on the Spooky Tooth site.
I use #41 Roller chain which is plenty strong, although #415 chain will also work. The 44 tooth sprocket works fine for me on a 26" cruiser. The lower the tooth count the lower the torque and the higher the top end speed.
Good Luck!
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