If you're trying to keep the cost down, a Super Six upgrade is easier and cheaper going to a 4bbl carb. You can even build your own 2bbl intake. See 2bbl intake for more info. I'm using a QuadraJet on my 225 but the 390 CFM Holley is widely used.
If what you finally decide on isn't available, just a wait a little while until another one comes up for sale.
