If you have a 2V (2-barrel) intake you'll want an Autolite 2100, with the proper calibration for a '66 289. If you have a 4V (4-barrel) intake you'll want a 1.08" venturi Autolite 4100, again, properly calibrated or as an acceptable substitute, a Summit M2008 in the 500 cfm version. Proper calibration means the correct jets, boosters, power valve, etc., for your engine. If your 289 is no longer stock (as in significant changes to intake and exhaust flow such as aftermarket cylinder heads or exhaust porting, then you'll need to experiment with jetting-up the carb as needed. IMHO, there's no reason to install Edelbrock Air-Valve-Crap except as a replacement to an original Carter AVS carb.