[84LX89GT]

My GT has 1.7 Crane Cobra roller rockers and at 120,000 miles i haven't had any valve float yet and i've had it up to 6,000rpm a couple of times (woops!). It's a good idea to replace them now since you're in there. The reason why is because with the larger pivot ratio you're pushing the springs down farther than they'd go with the stock rockers and when you start revving it any weak springs will have a hard time rebounding fast enough to keep the valve seated when it's supposed to be and you'll find out that your engine's power band seems to flatline at a certain rpm. That can be bad because if that's not at the end of the power band that's wasted power. Also, since you'll be having more spring travel, it will wear the springs out faster than they'd normally wear, especially if you flog your car often, so you may end up doing it down the road anyways. I hope this helped answer your question.