you could probably use a dart with that setup, but it will be tricky to get all of the drains working together, and not giving too much flow to one or the other, causing excess noise, or flushing in the drains. you might be better off looking for a external pump that will give you about 1500-1200 gph after head calculation. ive got a tank with 3 1.5" drains, and i still turned back a snapper pump running it a little bit. it also has a 75 gal sump. with the four drains if you can get them balanced out, you could prob run a snapper i guess.
if i had to re-do that tank, i would only use two drains, and a small 1500-1200 pump, with more flow used in powerheads or a closed loop.