So judging by the Google map you posted, the streetcar line was the 21 Tower Grove which was converted to buses November 3, 1940. There was a single track loop in Clifton Heights which ran south off Columbia Avenue. But the map I am looking at has no side street names. An on street loop means that single ended cars were used. St. Louis Public Service began using route numbers June 28, 1928 to facilitate traffic and to make it easier figure out which car was which the dark and fog.
The buses used in the conversion 80 GM TD-3603s #4900-4980 which were modified to resemble SLPS PCC cars. There is nothing like these on the market, but Corgi did do some larger GM buses years ago. By the way the 80 buses converted not just 21 Tower Grove but also, 95 Kingshighway, 20 Cherokee, 105 Gravois, and 92 Lindenwood.
The information is from several publications by Andrew D. young.
