Might be easier to comment if you could include some photos of the wood as well, just to give an idea of the 3D look.
I see the 2 "money" pieces as the 2d and 3d in from the left. And I see the choice between using the 2 pieces together as a single focal point - probably approx 1/3 of the way in from one side or the other, or placing them on opposite ends of the tank. The remaining 3 could be used well to complement the focal point(s). Make sure you check out how each piece looks from every angle, as well as the possibility of piling more than one piece together.
Another concern is whether you intend your tank to have a "flow" from one side to the other. 55s are long and narrow, and if you have plants like vals, and/or a strong current, that can cause the scape to have a sense of a left-to-right or right-to-left appearance.
Sorry if I provided more questions than answers!
55gal - Coralife 4x65w cf, xp3, flourite, Hydor ETH300w, pressurized CO2 w/ rex(TM) reactor!
30gal - 55W AH, ecco 2232, flourite/gravel, DIY CO2 w/ Hagen ladder
3gal - endlers/cherry shrimp
4W cf, Red Sea deco nano, flourite