Ok I have to put up my 2 cents on this again.
I feel that the 650 is a bit small for a built up 350 Chevy or a built 351. We have used 750 vacuum secondary carbs on our engines for years and never had a problem. The advantage of the vacuum secondary is you can tune it to the engines needs unlike a double pump carb. I understand Holley's table and why they share the information. The number of return carbs because of over carburetion was very high a number of years ago. I was also in the parts business for a few years in the early 80's and one of the biggest problems we had was folks buying 750 double pumpers for their street engines. Like duh they run like crap when you floor it and all that fuel shoots down the intake and floods the engine not to even talk about the over size jets they came with.
As to over carburetion fellas I run a 6 pack on a 340 in my 73 Charger. The factory set up for the 340 was the same as the 440 six pack. Center carb is 350cfm and both out boards are 500cfm each. You do the math that works out to 1350 cfm on a small block. HOLY CRAP BATMAN that baby must be way over carbureted by Holley standards!!!!!!
Ok so the car weighs two tons and runs 12's in the quarter and till I parked it I drove it every day to work and back. Point is with a vacuum set up you can get the advantage of a larger carb for spin up and still have it tuned to your engine size. Can not do that with a mechanical secondary.
That does not mean I would put a Domonator on a street car. My only point is that a 750 will work great on a 350 engine with out being to large.