I can't measure mine right now, but I can give you an idea. On my 290QB the lower bunk that's made from the table top is shorter than the top bunk because of the storage cubby at the back wall. It's about 5ft 9in long (I know because my head and feet nearly touch when laying on it). The other bunks are about 6 ft to 6 ft 2in. I believe the brochure lists them at 74 in. The distance between the top and bottom bunks is large enough for my kids (7 & 9) to sit upright on the bottom bunks playing beneath the top ones without hitting their heads (I'd estimate roughly 32-36in).
'14 Sunset Trail 290QB
Towed by a '15 Ram 2500 6.4 Hemi 4x4 CC
Equalizer 1200/12K (just because I still have it)