Many FE enthusiasts speak about the different head and intake styles used. In order of development: -Low Riser -High Riser -Medium Riser -Tunnelport
High riser and Tunnelport were race only and not available on your typical assembly line cars.
On Factory built cars: Low riser was the main style from the FE inception in the late 1950s until 1965 when the Medium riser architecture became the premier style. During the life of the FE 57-76 many heads and intakes were hybrids, the most notable example being the Cobrajet. It gets confusing sometimes as combustion chamber, port, etc were often mismatched in later parts.
Pictured below are Medium riser and Low riser 2x4 intakes. The Low riser technically had larger ports but as a general rule made less power. This is primarily due to the air and fuel mixture having to travel uphill to the head. It is generally viewed the Medium riser is a more efficient port which flows more and higher velocity. The included pictures really show how the bottom plane of the Low riser had to climb to get to the intake valve.
For what it’s worth, most people desire the Medium riser style, and rightfully so. But honestly if you are building a stock to 425hp engine, the differences in street performance are mild at best. Don’t ever feel that your engine is insufficient because you only have a LR intake.
I hope this was educational and maybe helped some newer FE folks to understand a few of the differences. As they say, a picture says a thousand words, so pictures: