Some sources for sub translations for the Heisei and Millennium flicks that AREN’T dubtitles are the Australian Madman DVDs and the Hong Kong Universe Laser DVDs.
The Universe Laser DVDs I’d be a little wary of because some look like they’re translated from the Cantonese dub back to English (the new Kraken subs for RoG are a HUGE improvement), but the Madman ones (namely vs Mothra) seem accurate.
The subbed copies that Janus/Criterion are using for their Showa titles are improvements over the Classic Media ones, too.