JTG, after looking at your photos there is something I don't like. The engine ground looks poor and not very well located. First the "grey" wire just looks to be redundant from block to block. Your connections SHOULD NOT be on the head studs. The soft electrical connections will not maintain good "torque pressure" as they will slowly yield over time. Take those connections to a starter bolt or the flywheel cover and re-torque the studs.
When grounding on the head keep in mind that the full electrical load is going through the head which is insulated by the head-gasket and relying on the stud which is fastened with sealant to get the ground to the block the ultimate goal.
Dave Neptune