@PG:
If you have a 68k,
WarpScumm is probably your only hope as it is the only version that does not use the regular SDL library and thus is fast. WarpScumm has unfortunately not been updated for a while though, so it probably doesnt support as many games as the more recent versions.
If you have a ppc which offers substantially more processing power, you can take a look at
this page for a WarpOS version.
/Patrik