I asked for advice below about overhauling a 77.  I'm going ahead with it.  Have the head and oil pan off.  My question is whether the nuts on the crankshaft end of the connecting rods are held in place by something.  

The nuts have grooves cut in them as if a cotter key could be put through to keep the nut in place.  But I see no cotter keys and in fact can slip the socket right over the nut.  But I did not budge the nut with a pretty hard pull.  

I can use a longer wrench handle -- but before I do, I'd like to know whether some device is holding those nuts in place.

Thanks for any help.