That is why I directed you to Friedman, there really arn't too many good side by side pictures. A few results from Googel Images
The pointer stands on the platform by the base. Another platform opposite for the layer (or is it vice versa)
5"/38
The 5"/38 was a dual purpose gun, capable of high angles. The whole gun crew, loaders too, are on the larger platform. Note the large rectangular breech vs the cylindrical one on the /51. Note too the different trunnions and the base. Totally different guns