The HP draw difference between an electric and mechanical water pump on a 200 is negligible. In fact, you're probably better off with the mechanical pump.
A mechanical water pump is very efficient at converting crank hp into impeller spin (you've only got belt/friction losses). An electric water pump still requires power to turn. Electric power, which is converted crank hp.
Alternators are about 50% efficient at converting crank power into electrical current. A real good lectric motor is maybe 75% efficient at converting that current back into mechanical force. So, it takes more than twice the crank hp to move the electric impeller at the same speed as mechanical.
The mechanical water pump draws -maybe- a quarter horsepower at max rpm, and the flow curve follows the demand curve. An electric water pump draws 7-8 amps, or about 100 watts, which, after conversion losses works out to about... a quarter horsepower, at all speeds.
What's the point? You'd probably pick up more power changing a dirty air filter.
The early single groove damper + water pump pulley combo is about 7-8% under-driven - compared to the late dual groove + water pump pulley combo. As mentioned before, the damper and water pump pulley are very close to each other. An underdrive water pump pulley isn't going to work, as there is zero room for one. You would need a custom made underdrive damper... $$$.
An underdrive alternator pulley... This has got to be one of the biggest jokes in the aftermarket. The alternator is a "demand load" device. The more power that is drawn off of it, the more hp is required to turn it. It doesn't matter much what size pulley you have on it, up to the point of ruining the effectiveness of the charging system. Ok, the mass of the stator does make a difference. A big delco 12si unit is going to pull a bit hp more than the stock 37amp unit due to this. But the alternator requires a certain amount of crank hp to produce the demanded electric load. At high rpm, the size of the pulley doesn't matter as the alt is spinning fast enough to charge, and the drag load adjusts accordingly. At low rpm a large pulley means you are running off the battery.
Dyno guys pick up (a little) power using under drive pulleys due to their larger diameter. The belt(s) don't rub as much making the turn around the pulley. On a 200, with a damper and only two pulleyed devices, it doesn't make much difference. On a modern V8 with a power steering pulley, two or three idlers, a smog pump pulley, high efficiency (drag) water pump, large stator alt/high electric load, and an A/C pulley, it makes a little bit of a difference. Remember also that dynos use cheap chips and temp/humidity differences though the day can result in different readings on exactly the same engine. Also, the resolution of a typical westech dyno is about 3.5hp at 6000rpm. That's an error factor of 7hp, run to run. Call it the magazine editor fudge factor (he sells advertising to under drive pulley makers...).
You would pick up a lot more "free" power by using a big electric fan instead of a mechanical fan. The mechanical fan draws the most hp when it is needed least, at high speed/rpm when ram air should be cooling the radiator, without needing the fan at all. At low speed/rpm, the mechanical fan is barely doing the job.
An electric fan, that's the ticket.
Rick(wrench) -my 2 cents-
