Mallard When you do the front floor(and cab mount i suspect) it needs to be bolted to the frame to do it correctly.After the floor and what ever else you change is done mount the doors and stuff to see if they still close well. Than i would just put it on the firewall to do the finish welding,the back of the cab will dent .Try to do most of the welding inside the cab and seam seal the underside,just looks neater in the end after you put a mat or carpet in.