I would prefer to not buy a unit that's combined,that way we can buy just one unit if need be,we are not looking for fancy options,we live in a farm setting and have three kids,we need a basic dependable set up,if any options it would be to be quick as we do a lot of laundry.

Well, the "tight space" might limit what units you can get, so you should probably measure and narrow it down first. I also would not get a "combo" unit, but rather two separate units that are stacked but operate independently.

Where's the door in relation to the long wall or short wall?

3' x 7' is pretty nice. How about depth???? You may be able to get a front load washer & dryer and stack them. They would give you the capacity you need. A single combo unit like the one LG sells isn't convenient since and LG says this it would take about 5 hours from wash to dry.

You can stack both LG and Samsung units, depending on models. There are probably other FL units out there like GE, Maytag, Whirlpool, Bosch Axxis and so on.