@TheBilgeRat
Depending on what version of you are using it could just be that its compiled newer C complier that produces binaries that don't run very slowly on a basic 68000.
I had that problem with the new test version of ADOM on my 68000 based Minimig but the older release version runs perfectly.
As I remember setting up and The Hitch Hikers Guide to The Galaxy again under Frotz on my Minimig I am sure it ran at an expectable speed for me on my 68000 Amiga clone.
... After a quick look around on the net I can only find the latest release, but you acn probably find older version on Aminet CD's from the 90's see
http://www.stone-oakvalley-studios.com/wordp_blog/?page_id=2209 but I am not suer which set would be best of if they are still available for purchase.