Doubt that you will find 8.5-30 - don"t think that size ever existed.
You may find some old stock 8.3-30 but I doubt even that.
Info I have indicates 7.2-30 (replacing original 7-30) is best option - currently made by Titan who bought out Goodyear Farm Tire business - still says Goodyear but made by Titan now.
I may need to double check, but my recollection is original G options were 6-30 (now 6.2-30) or 7-30 (now 7.2-30). I don"t think they ever had 8-30 (now 8.3-30) as an option.