There isn't a difference. There are pointers, but no definitive differences in HJ. HJ Holden is the same as HJ Kingswood too, ie virtually impossible to pick. The main difference between identity picking between Holden and Kingswood Sandmans is on later HJ's (5/76 on) with HX paint. On these metallic paint on a Holden ute or van is a good pointer towards being a Sandman, but not so with Kingswood as metallic was available on Kingswood. Earlier HJ's had metallic available acroos the whole model range.