Bob
There is a lot to learn about the 427 and all it’s variants!
I know very little but I will try my beat to help explain and guys if I’m am wrong PLEASE correct Me
The 427 Center Oiler was introduced in 1963 it featured low riser heads low riser heads actually have taller ports than “medium” risers
In 1964 ford introduced the High riser I believe it was on a center Oiler block as well but it featured a very tall intake port and a tall manifold hence the name
The “side Oiler” was a different block casting than all previous FE engines as all other types of FE engines are center oiling designs
The 427 side Oiler block was introduced in 1965
Somewhere around 1965 I believe the medium riser hit the scene I may be wrong in this statement and if I am please correct me.
There is also the 427 SOHC (the rarest of the breed) and the 427 tunnel port
All of these combos have intakes to match them as well
There is a lot more I am missing but this is the place to find info
I hope this helps
Dave