RE: NQD High Wind 757 upgrade
Running dual motors will decrease the available ESC's that you can use. Novak makes one (for the dual motor Villain EX) to name one.
If you are bound and determined to use 2 motors (I wouldn't) then go for the 480's. For efficiency AND noise reduction, I would put flex couplers (4mm to 1/8" I believe) between the motors and drive shafts. Get rid of those silly, loud plastic joints. You will also have to replicate the stock reversed wiring on one of the motors to handle the left handed prop rotation. Otherwise you will get bad torque steer. Did I mention you should probably use ONE good motor?
The stock drive shafts will dramatically limit your propeller choices as they are little 1/8" threaded units....someone else will have to pipe in regarding specific threaded props you could use. I would put flex shafts in teflon liners out the back to 3/16" drive dog units. This will be efficient, quiet, and allow many many prop options...although those motors (480's) won't handle much above 38mm.
REMEMBER...with a 2 motor set-up, you have to buy 2 of everything along the drive lines which can add up.
You will also need a real 2-ch radio sytem if you want to run a servo rudder set-up and an ESC. Get the Futaba 2-ch system (2PH-AM) for 41.99 at offshore electrics. You will have to build a servo bracket inside the back of the boat. As you will see, there are not a lot of places to screw things down back there.
For rudders, consider the one shown in the picture below...available at offshore for $9. Of couse you could get a nice milled aluminum unit too for a whole lot more $.
Before you do any of this stuff you should strengthen the transom on the outside AND on the inside to beef up the stock paper thin ABS. Get some Otey's ABS glue at Lowes/Home Depot to bond the ABS to your transom. You can get a sheet of ABS at Lowe's, which is disguised as a NO PARKING....or BEWARE OF DOG sign. Cut it with quality sissors or use a box cutter.
Good luck.