If the splines are long enough , you could probably lop 1 1/2 " off and run them.
I don't know how much spline you have engaged , but in most applications , it is under 2 " I think.
Cold cut them and stone the burr off and I think you'd be dookin in tall cotton.
The studs ???? not so much I think.
Drilling would be less of a problem than tapping.