No, you cannot directly swap an 87 Suburban transmission into a 96 Suburban. The transmissions are significantly different, incompatible in terms of both the physical mounting points and the electronic controls. The 1987 Suburban likely has a much simpler, mechanically controlled transmission (likely a TH400 or 700R4 depending on engine and options), while the 1996 Suburban almost certainly has a electronically controlled 4L60E (or possibly a 4L80E depending on the engine). These transmissions have different bellhousings, different input shafts, different valve bodies, and different control systems. Even if you could physically make it fit (a highly unlikely and very extensive undertaking), the electronic incompatibility would prevent it from functioning.
You would need a transmission specifically designed for a 1996 Suburban's engine and drivetrain. Trying to force an incompatible transmission would be a major, and likely unsuccessful, project.
