Give some thought before deciding to do a switch (not taking up for the e-clone, it may be the only carb I dislike more than the Rochester B).
How much city driving do you do?
The cam is going to absolutely kill fuel economy in city driving. While I would certainly agree with TJ that 17 (or more) MPG should be possible cruising down the highway; that figure could easily be less than 10 in city driving, especially this time of year.
Other issues which can hurt fuel economy: tires (bias instead or radial), tire pressure, a dragging brake shoe, and especially a bug screen on the front. Removing the bug screen on the front of my Dad's truck put there by a previous owner increased the fuel eoncomy by 20 percent!!!
The other thing to think about is payback. Consider the cost of any new carb, the number of miles driven annually; and you can determine how many years it will take to break even on your swap
Personal experience: I upgraded a single barrel Holley on my own 300 CID 6 to a 400 CFM genuine Carter, and went from 15 MPG to 22 MPG on the highway. City mileage also increased from 10 to 12.
The e-clone is a little large, but the primaries are SMALLER thus more efficient because of higher venturi air velocity than the 2-barrel Holley.
But the most important issue in this post is to consider your driving environment.
Jon.
