The 289s required over 90 octane. I want to say it was around 98 leaded octane, but my memory isn't that good. The heads need hardened valve seats to run unleaded or you have to use lead substitute. I used to put Outlaw octane booster in mine and noticed a difference.
Holley is the most common. I prefer the Autolite 4100 from Pony Carbs. They take the flat spots out of the performance curve when they rebuild them and the carbs are near maintenance free. They have a 480cfm and 600cfm. 480 is the standard 4v and the 600 is for HiPos. I have always run Autolites, maybe someone on here can give you suggestions on aftermarket.
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