disapoining et

Whatever you get for a holley carb, start very close to the baseline jetting that it came with from Holley. Most 4779 750DP's are in the 70-72 range primary with a power valve and 80-82 secondary. Easy to find and relatively inexpensive.

With a 1" spacer, lots of times they like to be jetted up ~2-3 steps front and rear. Test it at the track. See if it picks up MPH after jetting it up. If it did, you are headed the correct direction. Keep going until MPH slows down.

No power valve in that 660 carb you have which is another issue with driving around town. IMO, it may flow 900+ cfm if it got 3+ inches of vacuum drop... not the std 1.5". Can that 660 carb and move on to something more appropriate. If someone sold it to you knowing what you intended to run it on, they did you no favors!