To echo what Leigh said, the side range finder is a better choice. I was told by the retired Graphic and Graflex repairman from whom I bought both my cameras, that the top rangefinders has a nasty habit of "loosing their marbles". That is the ball bearing will drop out without a warning and that there are many postings on the internet asking how many ball bearing should there be in the top mount range finder. He gave me a choice of range finders, but he was quite adamant that I get the side mounted one, which I did.
By the way, the retired Graphic and Graflex repairman is on the board of graflex.org.