Tim:
Nice photos of the “real” thing over the years in St. Louis. Their PCC paint scheme is very similar to our Pittsburgh PCC's which BTW were all built by the St. Louis Car Co.
Re your layout plan, make sure you allow enough room for the D-21 Super/E-Z Streets curves plus clearance for the trolley overhang over the outside rails as it goes around the curves. You don't want to use D-16's as it would limit what you can run. A “Streets” D-21 circle measures 21½” across outside edge to outside edge. The amount of clearance obviously depends on the specific trolleys you are running but I would suggest you allow at least 1”. It looks like you have about 24” across on your planned oval so you should be OK.
HTH,
Bill
