Help! OCC Science GS Deity

I need your best science victory tips for OCC!

I have been relentlessly trying to win an OCC game via Science Victory on Deity with Gathering Storm rules, while only using Barbarian Clans mode. My best attempt was 20 turns short of winning with a 30+ pop Yongle city, Kilwa, Temple of Artemis, etc. I’ve come close with Portugal, Theodora, and Korea, but can’t seem to close it out even with 450+ science on the last turn.

HOW?! I like playing as close to vanilla as possible, so I leave out the heros, secret societies, corps, and mods. I want the playing field as level as possible, and yes, I see the irony lol. My last game ended after Gorgo nuked Poland and consolidated their resources, which boosted Greece to secure the Science Victory.