West coast drives have a very specific type of gearbox, which has the gearbox's output shaft directly connected to the center wheel (if it is a 6wd). It also has chain/belt running through the center of the gearbox (usually).
We built a west coast drive this year using the WCProducts 3CIM single speed WCD gearbox variants. Notice how the output shaft is to the bottom of the gearbox and there is enough room to place a 4in wheel on the output shaft and not have the gearbox touch the ground?
Picture of said gearbox
Link to said gearbox
If you are set on using that specific gearbox there are ways to get around the gearbox touching the ground by chaining the output shaft to the center wheels, but then the drive would no longer be strictly speaking a West Coast Drive. Or you can always use bigger wheels.
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