The Dumas stuff isn't that great so avoid it.
You can use parts for 6-12 cell electric boats if you stay with the OS. 10 . 1/8" flex cable with the 1/8" propshaft will be fine unless later on you decide to drop a better powerplant into it. The OS flywheel is what I use on my .12 boats and should fit on your .10 . Octura make a 5mm threaded flex cable collet for the engine also.
Check with www.fastelectrics.com in Oz as they may have the parts that you need.
I'd go with a larger hull than what you're looking at otherwise you'll need a shoehorn to fit everything in to a 19-20" hull. 22-24" will give you a lot more room to install everything.