also the 4.3L manufactured after September 1998 - the crankshaft has a deeper pilot hole to accommodate the longer torque converter hub - earlier 4.3L and small blocks (including the 85 and older) have the shallow pilot hub where the adapter kit is required since the torque converter will bind against the crank if the LSx based 4L60E (includes the 4L80E for LSx) is bolted 2 a traditional SBC