Did you look at both sides of the one I have and posted? It says 3400 on it and the cast in part number on the housing is the same as the eBay one. So methinks that some 3400's had one kind and others had the other kind. But I don't remember if this is a saw I parted out or if I got a bunch of misc parts somewhere along the way, so I can't be sure...
I also know that there tends to be a lot of variations in Poulan saws. Worked on the 2000 series for a while and was amazed how many different clutches, bearings and sprockets they used on those.
Your pulley is for a 4000. There were three different pulley designs. 3400 and 3800 shared one and the red Craftsman 3.7's (3700) used that design as well. The 3700 and 4000 had different pulleys but the starter dogs are the same so they are interchangeable.
The only difference are the starter dogs on the flywheels. They are staked in place and are not offered separate from the flywheel. Maybe your 3400 starter cover came off a 4000 or a 4000 flywheel may have been put on the 3400. I have driven the staked in dogs and changed them out. They are a splined pin (like a wheel stud on a car) and can be driven out from the back of the flywheel.
Not sure why they stopped making the 3400 pulley as the last stock disappeared quickly.