Not the first time this question has been asked. Technically - Can be done, but to be done properly, it will take many hours. As Ian pointed out, you need to copy the lightboard in the backbox. Power supply board could be a repro (Greg stocks them) - so you only need a donor machine.
Personally, if someone asked me to do it - I would not. As a KISS fan myself, I would see it as fraudulent..But then again, if a machine I want to buy does not have matching serial numbers on the headbox / body, I would not buy it..So my view might be a bit "extreme"..
If you are going to invest in a title such as KISS, it should be original. Same goes for the "King of Diamonds" repro, or the rumored "Medieval Madness" repro - They are just as "Not original"..
A rough KISS is the best option..
