A "west coast drive" is generally a term referring to a drive similar to 254's drivetrain. IMO these things need to be present for it to be a "West Coast Drive":
- Six / eight wheel drive, with the center wheel dropped
- All wheels cantilevered
- One wheel directly driven, rest chained to that wheel.
Once you have these three things, you have something resembling a "West Coast Drive".
There are many different variations of even this drive, though. Some teams, like 27 and 118, cantilever the wheels on dead axles and tie the wheels together using chain and sprockets bolted to the wheels. Other teams like 254 and 973 use live axles and run their chains on the inside of their drivetrain, cantilevered off the back of the axle.
Tensioning is another system where differences occur. Many teams use sliding bearing blocks that move each wheel in order to tension drive chain. Some teams tension in other ways.
My team's (2791) west coast drive is really different enough that I'm not sure I'd even use the name. We cantilever our wheels on live axles, but we run timing belt instead of chain. Because timing belt does not stretch, we can run systems with basic idlers instead of tensioners and never need to adjust the belting after we get it right. In addition, for added security and to save space, we run the timing belt on the inside of our drive's welded tubing. This results in a very clean and simple drivetrain that has been remarkably reliable for us.