[Shotimes] please help...SHO related

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Hello everyone,
I have a 1991 SHO plus,(white)
What do you guys think could cause not to have any electricity in the car? I 
checked the fuses, tried a fully good working battery, a battery 
charger,disconnected the alternator  all the harnesses on top of the engine  
and i get absolutely NOTHING, no sound from the fuel pump,no signs of life 
on the car, not even the clock....  Any ideas or suggestions are greatly 
appreciated!

Thanks
Os