Yes and No, as a general rule many of the two-lever G&H top and bottom will match. A friend brought a rifle by last week with a G&H two-lever base and I tried about eight tops to it and only four went right on and locked down. He was looking for a top so we where looking how easy it was to fit. I would not suggest buying a top, say from ebay where you could not return it.
Other mounts like Noske are just about impossible to interchange. I have a early G&H 7mm with a Noske side mount that I have tried many , many mounts on without luck.
