When you are ordering on Boyd's web sight, if it says It's for a stagger feed short action, it's going to be a 4.25 spacing, if it says it's for a center feed short action the spacing will be 4.40,
as far as long actions go the bolt spacing is the same for both, they only difference is where the mag box is cut out, but you can trim one to fit they other, and finally there is a sporter stock thumbhole and a varmint thumbhole the varmint version has a lot more "meat" on it so you can channel out for a bull barrel,

Tanks Dean