A two or foul barrel carb is up to you.
Of course when you floor a four barrel your milege will be worse than a two barrel,,,, but you will make typically make more power with a four barrel.
Vacuum secondaries will give you better milege.
Mechanical secondaries will use more fuel & typically give you better acceleration.
I believe you will probally get better milege w/a Edelbrock carb over a Holley.
As far as tunning A Holley would be easier to dial in.
Most people can't figure out how to property tune an Edelbrock carb.
Remember, in a six cylinder engine ,,your vacuum will drop down lower typically than a V-8 engine.
So, I would nornally run a lower vacuum rated power valve or on the Edelbrock carb(softer springs)
To really tune any carb in nicely, you should get a wide band O2 reader.I use the LM1 from Innovate
http://www.innovatemotorsports.com/ much better than seat of the pants feel,A.K.A.(butt dyno) or trying to read spark plugs.
MBHD
