The question is "how much torque does the new engine make at the observed stall speed?"
It may have less than the original engine (later intake closing = lower CCP) and will stall lower despite the higher peak power.

If the stall torque is higher, the stall speed will increase (duh) by the ratio of (new torque ÷ old torque)^.5
RPM = K × (T^.5)
Just using easy numbers:
Stall now 3,500, new torque 550, old torque 500
(550 ÷ 500)^,5 = 1.0488, × 3,500 = 3,671 RPM new stall
Stall now 3,500, new torque 600, old torque 500
Same math = 3,834 RPM new stall

Whether this helps or hurts launch...?