Hi praisethelowered,
If the carb port is vented into the carb above the throttle plate it is a "ported" vac source. Below the throttle plate it a "manifold" vac source. I suspect it to be a "port" source as most carb vents are. What source was your dizzy hooked to pre-triple. Use the same source and you won't have to re-engineer the DII. Personally, I like a mechanical only set-up. I have converted my dizzy to mechanical. However, if you use the primary carb. for your ported source it should perform fine. If you need a manifold source you can "T" the trans line.
Carb tuning. While I do not have direct experience with the Offy on the 200 engine, I have a good deal of experience with multiple carbs set-ups. So my comments, while generic, will get you where you need to go. Fine tuning over time will be different with each car (cam, compression, condition, etc), so I am confident my generic comments will be useful. There are two challenges to initial set-up, idle and outer carb sync.
Idle first. The Offy set up idles on the center carb. However, the idle circuits on the outer carbs will be active, i.e., not closed. The best way to set up the system, initially, is to block off the outer carb attach flanges and tune the car to run on the center carb, only. Idle mixture, speed and timing. Note the number of turns out from the stop the idle jet setting is when done. When setting for idle with the outer carbs installed, because there will be additional air flow, you can't shut the outer carb idle circuit all the way off or the idle will be lean. However, you don't want them open to the level of the center carb, as this will be rich. So open them half way (1/2 the turns of the center carb) as a starter. Without hooking up the outer carb linkage, start the engine. It may idle quite well. However, minor adjustment to each outer carb, back an forth, could be necessary. Tune for smooth idle. Don't re-adjust the center carb during this process, and be sure the outer carb idle speed screws (throttle screws) are off, i.e., not open. These carbs should not be active at idle. The "system" is progressive.
Off idle. Because the outer carbs come in after, or behind the center carb, idle sync is a moot point. So the typical sync tool is of little value. The key is to have them open at the same rate. By full throttle all three carbs should be full open. Between idle and open the outer carbs need to be flowing equally, but this is not a critical issue, i.e., close is OK. The easiest way the set up a progressive system of this type (mechanical progressive) is the adjust the system to WOT. So, open the center carb to full throttle (engine off of course) and then adjust the outers to WOT at the carb. You will need to block the kinkage full open to accomplish this process. This done, since the system is progressive, the opening rate of the outer carbs will be equal, not withstand slop in the linkage. The next step will be to adjust the initial opening point. There are many variables here. Mileage vs. power, etc. Personally, I would set them up be begin opening at the point the center carb is 1/4 open. Live with the car and adjust from there. Be sure to double check WOT actually happens in the outer carbs when you're done with the initial set-up.
Jetting. Can't be of much help here. Main circuit settings will not impact the idle set-up. The main jets will probably need to be one or two sizes smaller in the outer carbs. My educated guess is that since these carbs are designed / set-up for a smaller engine, the fact that you are using three may work in your favor. Ignition ping, running temp and plug condition will have to guide this process, over time, but I would start with what you have.
Don't let this process frustrate you. It is fun, challenging, and will be rewarding when you're finished. It could take weeks to sort out jetting unless someone using these carbs on a 200 with the same configuration can make a recommendation.
Enjoy the trip - Steve
