I will use metric on this, because I find it easier.
Your current spacing is .78125" ~ 19.84mm
19.84mm x 3 = 59.92mm (four strings means three gaps between them)
59.92mm / 4 = 14.88mm (four gaps for five strings)
14.88mm ~ .586"
Seems to me you need roughly 15mm spacing, which I have heard of some bridges pulling off. There are a few adjustable ones(Kahler makes one), or you could go with the individual bridges(sometimes called monorail bridges).
If anybody sees anything off in my maths just say so. I don`t want Zack to get the wrong bridge because I fat fingered a number somewhere.
Luna Pheonix - First Bass, still a player
Ancient Aria Violin Copy & Kent 70`s Super Short Scale- Projects