Never used it, but seems like a nice tool: https://www.holley.com/applications/CarburetorSelector/CarbSelection.asp
I didn't. I have a Edelbrock 650cfm waiting for an intake and apparently it is too much. The gizmo says I should have a 390 or a 570cfm. I gave away a Quadrajet out of a 454 Chevelle that had 2x4s. Maybe I should have kept it?
No you didn't get too big of one. The Edelbrock you have is just fine for your car they work differently then Holley carburetors, you can go with bigger carburetors with Edelbrocks, jet them to where your car is running properly and you will have no problems with it. Holley is a completely different animal in that respect, that calculator is the tool you should use if you wanted to buy a Holley carb, after all they are trying to sell Holley carbs not Edelbrock.
Well John I think I,m under carbed even though I increased the jets substancially. 72s in the front and 81in the back. Double pumper. What did it suggest for your 347.