it's strange eng. stuff. I was looking at a chrome moly spool at the spring fling swapmeet that I almost bought($125.00) but the guy was honest and told me that it was for 5.13-6.14 ratios and I would not be able to use it with 4.10's and a friend of mine said he had a friend that could set me up with a new one and new 4.10's for a good price so I went for it never thought to ask if I needed a spacer but I am sure he would have told me if I needed one. I'll find out
anyway it is 5 1/4" from the bearing seat to the ring gear surface area. and the new ring gear looks like 1 1/16 from the surface area( where it mounts to the spool) to the tall side of the gear. or the gear at its tallest point to the work bench is 1 1/2" does that make sence, not sure I am discribing it right Ron....
I thought you knew what a spool was 
never thought to ask if I needed a spacer but I am sure he would have told me if I needed one. I'll find out 
