I am trying to figure out what type of machines could be used to reconstruct these chips nowadays. It doesn't need to use exactly the same machines used to build them, it's just that the product should be very close.
I cannot find much about the original chips though. The 6502 has plenty of documentation, but I cannot find much about the original manufacturing machines used to manufacture it.
The 68000 is harder find, as it was manufactured by many different companies, so, not even I can find what was the original node. Wikipedia says the original was done in 3.5 um and Hitachi later shrank for a 2.7 um node.
It used HMOS, licensed from Intel: https://en.wikipedia.org/wiki/Depletion-load_NMOS_logic#The_HMOS_processes But, there was several versions of this process, so, I am not sure if there was any improvement to the node. (I would like to also reproduce those used in arcade machines and videogames, which used 7.5MHz, 10MHz an and 12MHz vesions).
For these nodes, it seems the g-line of lamp mercury was used(436nm). But some steppers are compatible with the h-line 404.7nm, which seems to be close to violet laser pointers (405nm), which are diode based.
It seems that these thick nodes could use contact steppers, but there is not much information about them. Perhaps their used ceased due to low yields? (that's all I could find).