Direct Connection ( Mullen LA ) heads

The correction factor to go from 3” to 28” is .327.
93 / .327 = 284cfm.

Which is also the result I got when I tried the Wallace calculator.
Thats a very respectable # from a Vintage oem cyl head !!!!
One thing to remember is that this cyl head is ( NOT) the big valve Prostock offering Mullen also manufactured.
The book I have touches on those im sure those offerings were very impressive .