Same sump, but make it 48" long instead of 36" long. You'd still have room for the calcium reactor to be external, or you could put a reservoir in the extra space for top off.
The Panworld pump would fit, provide enough flow to get the water up to the tank and keep the pump external. The return section would be larger. Another similar pump is the red one by Coralife, which looks just like a Panworld to me. I would get a pump that has a good warranty & reputation, doesn't use a lot of power, and doesn't push too much flow through the sump.
In a few days, the next issue of Reefkeeping Online is coming out, and there's an article about sumps that should be in it.
