Hello and welcome to the forums. My 82 has the couch/bed over
the water tank in the same general location as your table set up. I had wanted originally to replace the 2 barrel chairs opposite that with a dinette/fold down bed...to accomodate my 9 year old, but we opted to redo the whole interior upholstery and keep the set up original. (photos are on the airstreamphotos.com companion site)
We looked into any number of couch configurations.
The Flexsteel couches seemed to be the best, and will generally fit most motorhomes- the problem I ran into was having that tank underneath and not being able to clear the water pipes which run into the sink area. i went to camping world ready to buy one they had in stock, but the clearance was not there. Flexsteel made the original furniture, and they no longer make a replacement. I tried salvage place,etc..
My wife and i sleep in the rear twins (like Desi and Lucy), and the kids get the front couch bed, with one of them on afold up mattress on the floor in that same area. Works out well for us, but I sometimes wish I had that GMC set up with the fold down bunk. By the way Campingworld's prices on the flexsteel were unbeatable by quite a bit.