There was a single ROM solution once sold on eBay with both 1.3 & 3.1 KS programmed into it and switched with line going from the switch to the ROM pins. I bought one that now sits in my A2000 working fine, but I can't tell you any more. It is stored away in a box in the room I use to hoard ceramic trolls (much quieter than the ones on this forum), flash frozen small mammals, snails feeding on carrots to make halloween treats of, and various stuff I would sell were it not for the financial loss from what people who call "collectors" hoarders because they won't pay what the stuff actually costs.