Did you build the 289 (hyd. roller) in a late model 302 block or is this a retrofit (hyd. roller) application in a early block? Are the heads stud mounted rockers or shaft mounted? - just curious - You should call Comp or somebody like that with the specs.
Don't guess. I would recommend buying or borrowing a pushrod length checker every type of head/block and cam combo is different. Never buy your pushrods and rockers at the same time unless you're just freshening it up and not making any changes. Your local speed shop should have one, of not check Jegs or Summit.