You have to replace the kick panels to attach the door posts to it. spend your time on the door posts. Screw everything together with sheet metal screws first, 'cause you'll re-fit everything 4 times. Don't rush it, cause your doors need to close, and line up. When I did mine, I tore the cowl off, and left it off until the end. It let me see the top of the kick panels and allowed some easier welding. It is recommended that you put the hard top on, and bolt it up, because everything will want to sag, and the roof holds the windshield up. Measure from the floor to the bottom of the old dash, twice and write it down. I marked on the dash and the floor where I took the measurements so that everything went back in square. Don't take this job lightly. Going in over-cautious and planning to spend a day setting door posts makes for a better experience. I hate cutting out tack-welds. Use the self drilling #6 lath screws from home depot. I'm surprised all this front end metal is needing replaced but your floors are good? Lucky for you. When I cut my floors out, I opened up Pandora's box.
Long response short: kick panels, door posts, dash, then cowl. Let them sparks fly!