Man, I hate it when someone here starts thinking! \:D My ADD/ ADHD & CMMOB all kicks in at once. SBC- 3 1/2", 292 Chevy 6- 2 1/2", Stude V8- 3 1/4" GMC 270 3 1/4" I don't have any heads off the Cadillacs. These are just tape measure quickies.

Are you thinking 2 V8 heads or some other 6 also? Stude, Ford, IHC, Chevy a ton of tractors. How about British 4s? Have you considered overhead cam to just avoid the push rod thing?
Did you see the pictures of the Edgerton conversion I saw at Bonneville? Someone posted a picture here. You are welcome to come work on some of my projects! \:\)

"I wonder if God created man because he was disappointed in the monkey?" Mark Twain