225 Push rod length.

When you cut the tips off, I ground the tube right under the hardened tip until it started changing color. I chucked them in a drill press and just held a flap wheel on a grinder to that rotating area, quick work like <10 seconds each. Then I grabbed the tip with a pair of pliers and just pulled them out. Youre left with a mangled tube end but your trimming that part down anyway. For a .125 adjustment, you have very little to work with. I cut them down about an inch from a 225 to a 273 size so I had lots of wiggle room. Maybe if you took a hack saw blade and cut the rod at <.125 and then removed the tip from that 1/8 inch stub, it would be more precise. Finish grind the rod to .125 spec (or whatever you find you need) and them push tip back into rod (heat rod to expand and push in)
Dont know what the lift on the stocker is but your .125 shorter already. Add the dropped base circle, and your max lift is still .125 higher on the rocker as the lobe crowns dont usually change from the cam bearing datum. If you factor in the smaller base circle of the performance cam I think its gonna be -.125 plus the lift difference to give you a <.125 shorter pushrod. If That sounds right, I'd not try to use any formula, I'd get some adjustable pushrods or some 3/8 allthread with a coupler and mock up a pushrod length that will give you the same amount of threads showing with the new lift and go with that if that makes sense. Watch coil bind.