If there's no noticeable stumble or hesitation, it's usually not the carb. A good free-flowing exhaust system helps, as well as a cam designed to maximize economy.
Also, if you drive like there is an egg under your right foot, you'll get better mileage.
edelbrock has a square flange gasket fo it
Yes. Consult Edelbrock's website for specific details.
on an edelbrock 350 ? you mean Chevy 350 with edelbrock parts on it ? try the valve cover. open it up by unscrewing it or it may be just a pop of cap and puth the oil right in the valve cover just like every other 350 .
Check with Edelbrock to see if they offer the correct adapters.
10-12 degrees
The Edelbrock carbs work very well right out of the box, so if you have the correct intake manifold it should bolt right on with no problems. The Edelbrock website has all the info you need for tuning and connectivity.
12 mpg
id take the rocket my self it has a little more power than the Chevy 350
yes, from either jegs or summitt etc. made by edelbrock, and one by holley
600 cfm no 1406.
8-16 mpg
The 600 should give better throttle response, whereas the 750 should produce more horsepower above 5000 rpm. Most people are more satisfied with the smaller carb in these situations.