[camerjeff]

I was told it was a cost cutting move, Pontiac was being pressured to drop the OHC-6 and purchase Chevy I-6's. Chevy was making the case they could provide the chevy 6 at a price lower than Pontiac could build the OHC-6 and Chevy could still make a profit. Pontiac made many small changes to the 69 OHC6 besides the water pump.

The Water pump change eliminated many parts besides the bypass hose, there was the thermostat spacer, 2 hose clamps, and the fitting for the bypass hose on the water pump. The machining changes to block line consisted of drilling 1 more hole in the block for the internal bypass.

Besides the water pump they also

(1) replaced the cast aluminum rear upper timing belt cover with a stamped steel one. This also required the larger fiberglass upper cover to be remade with 2 bulges to screw the new cover onto.
(2) Replaced the upper timing belt cover mounting bracket that bolts to the front of the block and held the cover with 3 Mounting screws. With 2 Threaded stand offs that thread into the smae 2 holes in the block that the bracket did. And reduced the front upper cover mounting screw number from 3 to 2.

They also made some minor changes I forget at the moment. These changes required the modification of the following parts

Timing Belt front cover
Water Pump Pulleys
adding a flange on the timing cover to accept the thermostat without the spacer.
Replacement of the water pump gasket with a new design to use the internal bypass hole. It would also replace the 66-68 design as it would work with either water pump.

The changes eliminated about 10 parts from each engine made. The change in water pump shaft length was to prevent the installation of the incorrect water pump by mistake.

From a conversation with Fred Simmonds years ago.
The water