[Darel]

I have a '61 T-Bird with a '66 C6ME-A block (most likely a 390, but will check crank eventually) and original '61 "dressings" (at least the carb and accessories). As far as I know it's stock but since the engine was swapped anything is possible.
Anyway, I'm going to replace my factory carb. I have 2 options I'm looking at, and I need your help deciding. This car is my daily driver, and I want a definite performance boost but not at the expense of driveability. I'm looking at the Holley 4160, #80457S, with electric choke, vac secondaries, 600 cfm. For about $60 more I can get a Holley 4150, 650 cfm, vac secondaries, elec choke, #80783C. Like I said, I'd like that performance boost, so I'm inclined to go with the double-pumper for the extra 50 cfm and the added secondary tunability, since $60 more isn't too bad. What I would like to know is will it bolt on to my car just as easily? It's got an auto, should my factory kickdown linkage bolt on? Will the HP boost be noticeable, or not worth $60? Similarly, will the gas mileage drop be as noticeable too? Finally, since I live in Montana and this is my daily driver, will either carb cause me any sort of cold-starting problems?
Thanks for your advice. I think I finally have it narrowed down, just help me make the last decision...
Darel