Looking at brochures, I see nothing to suggest that older ones used HiAce - in fact most seem to be listed in brochures as HIACE or in some cases HI-ACE.

The use of HiAce seems to be enforced by English wikipedia, but in every other language it's Hiace. On the page of Toyota Hilux (listed that way) it says: (also stylized as HiLux and historically as Hi-Lux) - I think the same applies to the Hiace.

Then, there's the TownAce/LiteAce, which seems to always have had one correct spelling: TownAce/LiteAce.