Below you will find configuration and typical data for the command set test sets that may be useful. As you can see by comparing the first and last, there are some small variations over the years. It wasn't until the "Handbook Bench Test and Alignment Procedure for Radio Equipment AN/ARC-5" was published (NAVWEPS 1630ARC5-501 dated 1 October 1949) that a reasonably comprehensive treatment of the subject was introduced, but of course it was focused on the AN/ARC-5 and did not always apply to the earlier command sets.
This first diagram is from an original Signal Corps SCR-274N "Handbook of Instructions" produced by the Aircraft Radio Corporation under Contract Order No. 1470-NY-1941, with an initial order quantity of 4,000 in November 1941, and an additional quantity of 25,000 in May of 1942. This information is only contained on the cover and first page. Strangely enough, despite it being marked "Published by Authority of the Chief Signal Officer", I can find no T.O. or other Signal Corps number anywhere else in the manual. This is the only document I have found that reflects the I-71-B remote RF ammeter being used in the command sets, and sporadic brief mentions of it occur elsewhere throughout the manual. It seems to have disappeared in later versions.
The two diagrams below are from pages 147-149 of the latest manual I have from the SCR-274N series. It is marked T.O. 12R23SCR274-2 (formerly 16-40SCR274-5) dated 15 February 1943, revised 25 July 1956!