How did I miss this post! I'm the guy that converted his Cuda to EFI using the Ford 5.0 Mustang's computer years ago.
Welcome back!
We thought we'd lost you to Moparts. Your original post(s) was what started my interest in doing this...
You said you were doing a casting. Why not a hogout?
1. I want to try casting.
2. I have a local foundryman who wants to try it, too.
3. Cost, as always, is a concern. A hogout would require starting with a 4" x 9" x 16" aluminum block and milling 80% of it away.
4. In a non-supercharged application, I'm not sure that upper plenum strength will be an issue.