D'oh! I take it back, I thought the video DAC's were inside the custom chips.
Ah... I see a gotcha too. You need to also connect to the Alice chip too (or the 23-pin video connector) as not all the signals (Sync) are available on the Lisa!
We need to find a new low cost ASIC scandoubler/FF that has a 24-bit input....
Otherwise you'd have to do the design yourself and use an FPGA with enough block-RAM to hold a field of data (About 700Kbytes) or you'll have to add external DRAM and before you know it you'll have re-invented the FlickerMagic T