Yes they are the same. There are different ones for Autolite verses Delco starters. They too will bolt right up but if you change one you have to change the starter and associated wiring and the flywheel.
Here's one for an Autolite starter:
It's upside down but you can see the bearing in it for the Autolite starter shaft.
Here's the version for the Delco starter ('52 Corsair and later)
This one is right side up but it's clear the starter mounting is different - has a stud for the top and a hole completely through it for a nut and bolt on the bottom.
Delco type from other side -
On the Delco style there are "tunnels" for the top two mounting bolts. The other type for Autolite (sorry no pic) has "ears" on top which the mounting bolts go through.
But in conclusion, the one for the Autolite type starter will fit both four and six cylinder cars and the one which takes the Delco starter is the same for 4 and 6 cylinder cars.
