I cannot help Barry Bloor regarding his first question about the circuit at Rouen, but the enclosed map of the Reims circuits should answer the second. The above map appeared in a detailed booklet published by the Reims AC in about 1959 detailing the improvements made to the circuit in time for that year’s GP.
As far as I know, only two versions of the circuit existed, the first (from 1925) going through Gueux village and then up to join the Reims Soissons road RN31 at la Garenne and the second (from 1952) bypassing Gueux and extending out to join the RN31 at Muizon.
I am, yours, etc. Chris Nixon, Richmond