Yep, The Land was originally going to look (from the front anyway) more like Imagination, but with more pyramids, and more abstract shaped ones (think crystals). Imagination was roughly as it is today (this is `78-9) but with a more diagonal footprint - that is the pyramids would be more offset from eachother, and with an overall more `70s future look - Space Mountain style spires included! And the Imageworks would have a balcony outside the east pyramid!
As for where the respective pavillions would be - Seas and Horizons swapped places, The Land was going where Horizons went, The Seas was going where Imagination is.
BTW - The USA pavillion was going on the opposite side of World Showcase from where it is today, right where the main walkway. And it was going to be a circular concrete building - on stilts. You would have had to walk UNDER the suspended building to enter WS. Quite rightly, it was felt this was too imposing for the host nation. Quite how the American Adventures war wagon would have operated suspended in the air also probably had something to do with it...