[rooster]

Well, I climbed up over the rear axle and put a malleable tee between the brake line and the service brake relay.  Was alone so to be sure I had the correct one, I ran a piece of 1/4 inch tubing out to the left side and taped a rubber glove to the end.  Stepped on the brake and watched the glove inflate.  Bingo.  Rather tight up in there, and I ain't quite as agile as I was back when I attempted this sort of thing, but we got er done!  Still chasing air leaks, but mostly small stuff.  Thanks for everyone's advise and encouragement.    

Looking for a 3/8 foot operated air valve.  McMaster has one, but it is 1/4 inch and that will restrict the Locomotive horn a bit too much.  It likes 1/2 inch, but 3/8 will do the job.
                                                                                     Pete