[Rick Parker]

Dennis:

These are very unique carbs. The main body has different sized venturies for primaries vs secondaries much like the rare 700 cfm Holley. Drop leg boosters, Lemans Bowls (precursor to the current center pivot type). The base plate is similar to other 650-700 vacuum secondary carbs. The attachment point for the linkage is unlike other Holleys though. The small 5/16" diameter transfer tube feeds fuel to the rear bowl since there is only one spot to attach the fuel line on the primary bowl. This tube is the achilles heel for a real stout high winding 289 or one that has had the displacement mysteriously enlarged ie: 331/347(????)
The sizing (715 cfm) is considered by many to be too large for a 289 but since the secondaries are only opened by demand (vacuum) from the engine they work pretty well. They also allowed the modifications done by Shelby to the GT-350 to conform the the SCCA & NHRA rules of the day without major carburetor modifications.

Rick