I'm having issues with the electrical system the car sat for 15 years in Storage now it seems as though I have intermittent electrical system problem's working and not working turn singles instrument cluster wipers fan motor can anyone tell me where the main engine ground and body grounds are

 

I believe that there is a main ground wire between the battery and the fuel rail area [near the firewall]. Also make sure you have replaced the old fuses with new fuses. Just because they look good and test good...doesn't mean they are good.

 

the main body-to-engine ground strap is under the front passenger side floor connected at the engine-to-transmission join and then to the chassis. I do not think that is the cause of the problems.

try troubleshooting one problem at a time.

1) instrument cluster: do you mean the gage lights? or are none of the gages working?

Try disconnecting the battery FIRST: then get a wire "toothbrush" at any autoparts and remove each fuse one by one, cleaning the contacts, do this in the driver's and passenger side fuseboxes, and in the 5-fuse fusebox in the engine compartment near the coolant tank.