[dsraven]

just in case you haven't been around a resto on a task force truck before, the doors get fitted to the cab without the fenders on. then the fenders get fit to that. there are shims under the rad support and the rear cab mounts in order to get things level with the frame etc. I suggest to replace those rubber mounts when you assemble the truck as the old ones are usually pounded out. the cab sits on the front frame mounts with metal to metal contact and that area can be shimmed as required, there is a dimension for the frame to floor in the assembly manual, and the driver's side front mounting bolt is used as a pivot point to get the cab square with the frame so the hood lines up proper. the rear upper fender mounts, at the cowl, are shimmed to get the fender body line correct with the door. these trucks were built as work trucks so as long as the doors closed and latched that was good enough. not a lot of effort or concern was placed on gaps etc. the rad support to fender mounts get shimmed for side to side clearance so the hood will fit down between them well and the hood also has rubber bumpers on the sides so it doesn't take the paint off. the hood also has the X brace under it which helps adjust the width of the hood at the front and also helps keep it from being floppy and twisting. the door hinges were sometimes bent to make the door fit so if you can get away with rebushing and pinning them that is a great idea to keep the door fitting better. I have had a couple of these units and a great fitting door from one truck sometimes is waaay outta whack for fitting a different cab. I currently have 6 doors and one cab but only 2 of those doors fit the cab sorta decent. not great, just decent.same with the front fenders. lots of guys add or subtract metal to the edges of the panels to get a tight gap but bear in mind that the body flexes so too close a gap means body parts touch sometimes. when doing your frame and suspension remember that the cross member under the rear of the engine is important to keep or replace with something else in that area because frame flexing in that area makes the cab mounts move and that messes with the cab metal and can cause lots of problems wit metal fatigue and cracking. try to keep the frame supported in that area if possible.
and always post pics, we love to see the progress. ask questions if you have them. you will get lots of answers and you can filter through them to get your information.