The involute equation doesn't change at all. For standard module, basic rack, profile shift (if needed this is standard as well) and tolerances see spline standards (ISO 4156, DIN 5480, ANSI 92 (M)). Be sure you read the tolerancing system as well, since the generated spline will have "basic" dimensions (MMC condition for internal splines).
By offesting the curve you should get the desired result. When you add addendum modification you are just offseting the basic profile. Think of the string wrapping around the base circle: if you offset the profile you cut o small piecefromthe tip of your string. That's the same thing that happens when you shift the generating rack!
To get the correct measurement between pins create the cut with an offset, then using a feasibility study fing the right value for your offset. This should do the trick.