Why don't you use two eproms, one for each 7-seg display? It would cost
less than any other no-noise solution... no clocks, no processing, no
multiplexing, no nothing. See, eproms are being used for several strange
solutions where you need 8 output pins with up to 16 inputs... it is a
nice programmable logic device... by low cost.  You can feedback some
outputs to be part of the addressing, and automatic tables can be
created, just a whole use of imagination. :)
Wagner