Well, it's welded in. Connected to radiator support. Battery ground goes to both block and radiator support..
I originally did not have good ground and no start when I put that ecu in new after painting the bay. I had removed a little paint and it fired right up. 5 minutes ago I added a star washer under one side of it to give a little extra bite. So at this point I am confident that there is N.F.Way that it ain't grounded.