Thats not really a problem.
don't use ACC to create the offset.
use the DPTR.
the result of a multiplaction is 16 bits wide, so you multiply the hex
value of the key by 8,then add it to the base address of the lookup.
this is a simple 16 bit addition and the result of the addition is moved
to DPTR and ACC is used for accessing the 8 bytes.

Christian