The folowing are the instructions for mounting the head om my Model III. ( I have edited the instructions for clarity.)
To install the enlarger head carriage on the column, first rotate the nonslip, textured hand grip of the raising/lowering control counterclockwise as far as it will go without forcing. Look inside the carriage shaft way to check that the friction lock and its washer are far enough to the left to clear the right front rail of the column. If necessary move the washer to left with your fingertips (Fig. A)
Remove the top plate from the enlarger column.
Next rotate the upper spring counterbalance tape on the enlarger column so that it’s hooked end is toward the front of the column. It will remain in that position. (Fig B.)
Lower the carriage gently over the column so that the front and rear rails on the right side of the column will fit within the upper and lower grooved rotating bearings at the front and rear of the right side of the carriage shaft way. (Fig. C)
Check to see that the hook at the lower spring counterbalance tape has engaged the lower bearing shaft at the rear of the carriage shaft way. Now rotate the upper spring counterbalance tape to the rear so that it’s hooked end hangs down at the rear of the column at the rear of the shaft way, and continue lowering the carriage over the column. (Fig D.)
Press the carriage down gently along the column, and the upper spring counterbalance tape’s hook will engage the upper bearing shaft at the rear of the carriage shaft way. Lower the carriage on the upright by pressing down against the resistance of the counterbalance springs and lock the head in position by rotating the textured handgrip of the raising/lowering control clockwise.
Place the cap plate on the top of the upright and tighten the retaining screws finger tight.
I would post the figures but I'm waiting for the film to dry before scanning. Expect images soon.