RLS Sight Height?

[Black Fly]

Don't know if this should be here or on smithing forum. I need a replacement sight front sight for my Mark I 77 RLS. Before I go on my search, I need to know the height of the original. Was also wondering if the RSI sight is interchangeable with the RSL tang safety rife sight. It sure looks like they just changed the stock on these rifles. But looks can be deceaving.
Thanks
Bfly