My 51 Chevy sedan (with a 235)has the jaws on the balancer also, but no access hole in the grill, so I'm guessing at that point, they were just using up the balancers they had left.
The cars might have been different but my '51 1/2 ton truck w/ 216 has the jaws and the hole. Its a bit hidden by the chrome but the rear grill and the lower splash apron both have the hole. ...just used it the other day to spin a couple valves free after a good soaking.
http://farm6.static.flickr.com/5185/5695931707_78aab69b57_b.jpg
