Hi Hugh i hope you don't mind me answering for Jim, I am not sure what pin you are asking about, however I have rather battered one of these trucks still in pieces for a resto, there is a 1.7 mm .067 inch pin to the rear of the cab base the artic trailer is hooked on to this, both mime have crimped ends I just filed off the crimps a litttle at a time until i could drift out the pin and the trailer and cab section come apart.
The artic part is a different thing I very gently drilled the edge of the pin until I was able to prise the plate off, I did not really want to lose the shaft completely as there is also a washer assisting the trailer to swivel, however I presume that this could be replaced with a rivet or a philips screw as it is hidden behind the cab base plate and can not be seen, once the unit is re assembled.
No doubt Jim has a much easier way of doing things I just make it up as i go along.