The jack knife sofa/sleeper in our 2307 Classic was pretty uncomfortable when we got it - in addition to the joint between the back & bottom, the bottom cushion had been replaced with high density foam but the back was original, so the bottom was very firm and the back very soft.
We replaced the foam on the backrest with foam of similar density, then had a full width 2" thick "topper" made of the same stuff with a cover made of automotive seat upholstery fabric. The person in back still has to crawl over the one in front to get out (usually not a problem - wife's a very sound sleeper who rarely wakes up during the night), and the bed's super comfortable. Since it's only the two of us, we leave the bed made up full time.
2307C / 2002 GMC Sierra 1500 ext cab (BellTech lowering kit, AirLift load-lifter air bags on rear axle, on-board compressor)