I welded braces from the cowl to the inside top rail of the bed, between the door hinge post and the striker post, and side to side on the top bed rail.
If you are still bolted to the frame and you should be fine on height, but I would recommend replacing body bushings before you start cutting panels out, that way you have a consistent height front to back. You'll want to replace body bushings in front while you have the floors out, so you'll want to have matching bushings front to back when you weld it back together.
I also measured between the cowl and floor at the cross member to make sure that dimension remained the same.
I removed inner and outer rockers, front floor pans, tunnel and platform. Put all back together with screws, measured one million times, welded it up and it all fit, doors close well. Sometimes it's better to be lucky than good.