Looks like in 87 when the c6 and the zf were available, the zf had a 2 piece driveshaft, the c6 had a one piece. Looks like the other manual trannies could have been 2 piece or one piece.
Still not a definitive answer, but I bet your zf tranny is much shorter and used a 2 piece driveshaft.
133" WB, MT, 4x2, 2 piece (assembly), New Process manufactured
133" WB, MT, 4x2, 2 piece (assembly), Warner manufactured, T-18 transmission
133" WB, MT, 4x2, 2 piece (assembly), Warner manufactured, T-19 transmission
155" WB, AT, 4x4 (assembly)
155" WB, MT, 4x2 (assembly), New Process manufactured transmission
155" WB, MT, 4x2 (assembly), Warner manufactured, T-18 transmission
155" WB, MT, 4x2 (assembly), Warner manufactured, T-19 transmission
155" WB, MT, 4x4 (assembly), New Process manufactured transmission
155" WB, MT, 4x4 (assembly), Warner manufactured, T-18 transmission
155" WB, MT, 4x4 (assembly), Warner manufactured, T-19 transmission
155" WB, AT, 4x2 (assembly)
133" WB, MT, 4x2, 1 piece, New Process manufactured
133" WB, MT, 4x2, 1 piece, Warner manufactured
133" WB, AT, 4x2
133" WB, AT, 4x4, AOD transmission
133" WB, MT, 4x2, 2 piece (assembly), ZF manufactured transmission, (8-445, 7.3L)
133" WB, MT, 4x4, flange joint, Warner 1345 transfer case (flange output)
133" WB, MT, 4x4, flange joint, Warner 1356 transfer case (slip yoke output), (T-19), 6.9L
133" WB, MT, 4x4, flange joint, Warner 1356 transfer case (slip yoke output), (T-19), 7.5L
133" WB, MT, 4x4, slip yoke joint
133" WB, AT, 4x4, C6 transmission, flange joint
133" WB, AT, 4x4, C6 transmission, slip yoke joint
