Thanks.

Thanks Mitch.  That looks like the Dorman coupler, I was wondering if the original gm coupler was more similar to the 66 coupler.  I got a spec drawing the the original 66 and 78 truck coupler last night from Jim Shea, a steering expert on TC.  I am now looking into how to take some of the parts from the 66 coupler to make truck coupler to   look more like the 66 coupler. Thanks again.