Return pump recommendation?

Can anyone recommend to me a good return pump? (I'm planning for a new build sump w dimensions 42" L x 16" W x 16" H) with my 120 gallon tank?
Any opinions on whether an external or submersible pump is better?

Ok I am new to this so if you are asking feet of head, I think that is referring to the distance from the return pump which would be down in the sump up to its highest point before the water drops into the tank correct?
If that is the case then we are looking at 5.5 feet of water column (goes up into the canopy to distribute back down to one sea swirl 3/4" on the far right side of the tank. That's the plan anyhow) On the left side of the tank (the tank is 46"L x 24"D x 24"H) it has the overflow in the center of the left side glass panel so that the tank is a peninsula configuration so that it sits in the middle of the room and not against a wall but no plumbing is visible due to the cherry wood cover on the left side which covers up the back of that overflow.
The overflow has 2 holes drilled. One hole is 1.25" and one hole is 1" and both will serve as output to drain down to the sump (originally the smaller hole served as the access for the return water but with the addition of the seaswirl I'll plumb the return water line up through that cherry cover that goes from the base to the canopy.) Hope that makes sense.

The problem with the old sump is that  there is not enough room for the skimmer that I just bought and there is no refugium in it and used bioballs and was really setup for the previous owner's freshwater fish which will not work with my plans for the saltwater setup which is the reason for the re-design