I've seen some discussion recently that you could
put a complete 6600
into a high end FPGA. That would be neat. I haven't heard of that
being actually done, though.
As the 6600 was entirely built with discrete components, not chips, and yet
had to
be physically relatively compact, I doubt if it had much more than say
20,000-25,000 gates.
Nowadays that isn't anywhere near high end of the FPGA ranges.
Andy