I don't know which is the negative side of the coil, i don't have HEI the coil is seperate but its the stock coil and there are pink and white wires coming out of it, were can i splice in to it to get a ground for my MSD Tach Adapter to work

 

its the white wire closest to the front of the engine bay. My car didn't need a tach adapter when I put in my MSD 6A..

 

The tach adapter instructions should have that on them. In case you don't have them here they are.
http://www.msdignition.com/pdf/8910_tach_adapter.pdf

 

There are two which one

 

You'll have to use the first diagram. The adapter wires came with connector for connecting to the end of the wires that are wrapped in electrical tape. Those are the white and red wires. In my install I had to splice into the wires about 12 inches from the MSD box due to the mounting locations. Just match the wires, white to white and red to red. The red is for the ignition and the white is for the pick-up. The wires that go to the coil are inside the hose-like insulation.

 

I don't have an MSD BOX my tach started going haywire when i would put the pedal to the floor, so the guy at the speed shop said it would solve the problem, I have it hooked up all except for the neg. side of the coil, thats the wire i am looking for.