340 build - last time I "axe" these questions

If you don't have the heads yet, save your money and go straight to the eddy's. Don't waste money these days on iron heads unless you already have them. Carb wise, I have always loved Holley DP's for hot street cars. I have a 750 on my 383 now. Check ebag you might find a good deal on a 650 or 700 because there isn't as much demand. A 750 wouldn't be out of the ballpark, though and I would jump on one if you can find one at a fair price.