I have a stock 260 and installed a Edelbrock Performer 289 "low rise" manifold
and Edelbrock 600cfm carb with no driving problems 13 years ago. Some have
told me that 600cfm is too much flow capacity for the engine but the car
drives fine with the larger carb. One problem I had was heat soak and a 1
inch plastic spacer corrected that issue.
Jeff