Whisper of the Heart is in Ac3 in the Ghibli Ga Ippai boxed set, so is on your mark. And Mononoke Hime was released separately in Ac3, all on laserdisc, not to derail the thread. Mononoke is 1998. and the big box set is 1996.
The only other AC3 is the English Dub on Kiki from Disney in 1998 also. Just talking laserdisc, not dvd or blu-ray.
Howls was Dolby 6.1 EX. And Spirited Away was DTS ES. 6.1 I no longer have those DVD. on the first Japanese DVD.