Is it better to mount electric fans on the engine side or on the outer side? Do I want to 'push' the air or 'pull' the air?

Mount them inside (motor side) so it pulls air through the rad. If you mount them in the front you are blocking some portions of your rad.

If you plan on keeping the stock fan setup, and adding an additional electric fan for cooling while slow cruzing or such, you can mount the fan as a Pusher.
If your going to replace them completly, install them as a Puller.

Shrouds are used to guide the air to the standard fan. Since most electric fans bolt either directly to or fit snug against the radiator, a shroud isn't as necessary. High performance aftermarket (and factory) fans usually have their own shrould built around the fan.

I remember reading somewhere that puller fans are in the neighborhood of 20%-30% more efficient. Both of the above are straight poop. A pusher (as your only) fan may even cause more problems that it solves if you get one big enough to cover the radiator face. At higher speeds (over 45-50-or so) it'll block more air than it pushes through. If you use a pusher as an add-on to your regular fan, get one small enough to fit 30%-40% of the radiator surface and mount it as close to the lower hose outlet as possible since that's where the hot water from the engine is being pumped into the radiator from.

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