Are the 2 3/4 in bulkheads both drains, returns, or one drain one return? And if they are one of each are you sure they are both for 3/4 in bulkheads, and one isnt for a 1" bulkhead?

Before you figure out how much flow your pump can return to your tank you need to figure out how much flow it can drain. A standard 1" drain can drain up to 600gph. HOWEVER if it is a 3/4" drain it can only drain at a safe rate just around 330-340gph.

So depending on how big your drain is or if both your bulkheads are for drains then you figure out what your head pressure will be (how high will the pump pump, and how many 45 and 90 degree angles. for every 180 degrees worth of angles add 1 foot to the head pressure. So if your tank is 5' above the sump with 2x 90 degree angles figure your head pressure to be 6'. Then find a pump that can do the gph that you need and at the head pressure. I would go one size up and put a ball valve on the output side just to be sure you can have full adjustment.