When I bought my replica (I believe it to be a box-stock 5.0HO from a 1989 Mustang GT) it had a Holley 780CFM vacuum secondary carb on it (3310???). It ran like a pig. I swapped it out for an Edelbrock Thunder (the smaller version, I think) and it runs like a scalded-ass ape now...bigger is not always better.
On the other hand, you have some go-fast goodies on yours that I do not have, so you can most likely handle some more carb.
Have you considered a custom built carb? Blykins can take your specs and have a QF made that might just be the ticket.
Cheers!
Dugly
