Im putting a 1968 390 in in a 1968 f100. Motor came out of a 68 galaxie. Im putting flotech headers on it with a c6 behind it with 3.50 gears. Has a aluminum intake. What carb is recommended for this set up.
A 650 cfm is ok, but keep in mind, if your going to use the vehicle for cruising, daily driver, work and back, low rpm's...etc...a 400 to 450 cfm would be perfect. A 650 or more is good if your wanting to get maximum power. ie: running hard, showing off...this sort of thing. a 650 will work, but a smaller carb will be more efficient and easier to keep tuned.
It all depends on what your trying to get out of the motor....performance or effiency.
catskinners carb calculator is is good....80% is stock, 81% for what you have, 3500 to 4000 rpm ...normal driving. 6000 rpm if you run it hard.