C30 to 4x4 conversion?

[74CustomK20]

I've been thinking a lot of converting my c30 to a k30. I know the front core support mounts swap and that's what I'll use to center n find where the rear spring bracket mounts go (plan on a 52" spring swap at the time) my problem is the crossmember. Everywhere I read I see people swap em out... Why? Plan on about a 8" lift or so anyway so don't think axle will hit anything... Anyone know why? don't plan on a different trans, keeping a sm465 regardless...