Nice bike! I think you can put on whichever you prefer and be fine. Some go by preference, they like how the bigger tires fill out more. I really wouldn't be too concerned about which is "correct" on this bike. I had a high dollar '87 GT Pro Performer last year and the consensus then was to put whatever on it. I went with some really nice Panaracer HP406s:
https://www.ebay.com/itm/254401231955?campid=5335809022
GT recently re-issued some of their heritage tires, pretty cool! Though supply has been spotty or else I would've got some LP5s. Check em out here:
https://www.gtbicycles.com/usa_en/goods-gear/bike-parts-components/tires
If you didn't like my answer, you might try over here. Nice guys and knowledgable!:
https://bmxmuseum.com/forums/viewforum.php?id=25
Have fun!