Is there a way to change or add couplers to the rolling stock I have?  Seems like a lot of the DLS ones and a few default ones have a gray box where a knuckle coupler should be?  Some of the others that I figure are older versions, I want to change to a better coupler.  Does the rolling stock configurations go down to couplers, since you can change bogies, I thought maybe couplers can be fixed, too.
Thanks in advance,
Paul
				
			Thanks in advance,
Paul