I 2nd the 650dp. Another consideration would be a Qjet modified by Cliff, do a search over on Performance Years forums. Plenty of performance, great economy.
I'm running a full race 750dp on my 383 Pontiac, but mine has all the tricks and it's running on E85, so I needed the volume to go with the increased appetite for the go juice. I don't know what I get 'exactly' for mileage, but I top it off every 100miles...the factory gas gauge works like crap even with a new sender.
