To get to the down pin you must pull the fan, the fan idler, the harmonic balancer and the gear case cover.
To look something like this:
The dowel pin is located between the two largest gears on the left side.
This one has moved a little, so take a punch and drive it back in. I then modified the second gen tab to cover the pin and hold it in.
Any exposed bolts (like the one next to the dowel pin) remove; add some locktite to the threads and tighten to 18ft/lbs.
When you reassemble you’ll need a gear case gasket and a front main seal kit.
Tap the new main seal in with the provided metal ring to set the depth and leave the plastic thing in the middle. When you install the gear cover line it up with the crank shaft and push the plastic thing through. The seal should be properly seated.
3904353 Front main seal kit
3914385 Gear case gasket