Actually now that I think about it I added the strap when I replaced the head (the memory is the first to go). That was long before swapping engines. I remember adding one because I could not find one. Like you said it could have rotted off or been removed by the PO.
Remember this one was originally a fire cheifs car. They added a second battery and alternator to run the lights and radios. They may have removed it when they removed the second battery and stuff.

_________________

I got mine all hooked up and now it is working great. I didn't need the additional ground.