That would be the Tupolev ANT-20 Maxim Gorky. As of yet no kit exists of it in any way, shape, or form. Scratchbuilding one has been on my "to-do" list for quite some time now. The wings may be built using the same method as the ICM TB-3 kit (ribs and spars covered with courrigation) while the fuselage may be practical as a solid-balsa form covered in more courrigated plastic.
Luckily for anyone interested decently detailed plans of the ANT-20 do exist.
But I'm getting ahead of myself. You set yourself a worthy goal. However, to REALLY complete it, you would need a WHOLE lot more entries. I recommend "Giants of the Sky" by Bill Gunston. It's got about 100 aircraft which he qualifies as giants. The recognizeable B-36 and Spruce Goose is listed among the not-so-well-known Lockheed Constitution, SSW R.VIII, and nearly the complete line of Tupolev giants. Really a must-buy if your into giant aircraft like I am.
Let me tell you, though- you are off to a great start.
(Just a small tip: Your building skills are excellent. Now may be the time to play around with some weathering. Start subtle- pencil lead is your friend. I use it powdered to represent exhaust stains and in pencil form to detail panel lines. It's simple, subtle, forgiving, and realistic. Play around with it next time. Other than that, you look like your doing just fine.)