[Alaska Jim]

Here are the carb center to center spacings for the various Y dual quad intakes.

Edelbrock FM255 – 8 ¾”
Edelbrock 257 – 7 1/8”
Edmunds DM-427 – 8 9/16”
Mercury ECZ-9424-C – 8 ¾”
1956 Ford EDB-9425-C – 7 5/16”
1957 Ford ECG-9424-D – 7 5/16”
Fenton DM-427 – 8 9/16”