Originally Posted by KCT1986

The 7400 series RD is great, but not rated for a 30T cog, 26T was the max cog per Shimano recommendation for most racing RD back then. No GS version of this if I recall.
Another option may be drop-out hanger extenders, which bolts to the existing hanger and make it effectively longer. Seen these on ebay for use on MTB for people who want really large cogs. Don't know how well these work.
In addition to XT & LX there was a DX line back then that was high quality and used on touring bikes with larger cogs.
Good luck.