This will, I suppose, be of no real use since I can't think of the source! But I remember an ST mag (probably Format, since that's the main one I used to get) saying ST= 16 32 and TT = 32, 32.
Also, and I'm not the most knowledgable about this and it's been a while - didn't the ST have a somewhat crippled memory bus? It didn't allow the full 24 bit memory addressing of the 68k if I remember correctly. What was the max memory in an ST again?
Cheers, may be wrong!