Why not? 20R came in 79-83 far as I know; 22R started in... 84? Came in Celiacs before trucks IIRC; but when I think 1gen Yotas I think 20R always. 20R intakes are pear shaped and there is a ton of info on this "out there" so it'll be easy to figure out what you have.
Post pics if you can; we all love pics.