re-doing a frame notch

I'm putting a 4 link in my truck, and when I junk my stock spring perches, my truck won't lay anymore, especially with bigger wheels (i'm running gangster 15's right now ) anyways, i didn't do the original notch in my truck, otherwise, i would've done it huge to begin with, but how do i get a bigger notch, without having to cut the frame off at the front of the notch and building a new rear clip? or do i have to?