The problem is TIME. This is not a couple hour task. I spent an entire, and I mean entire, weekend realigning my doors/fenders/hood. It wasn't just slapping it on. There was body hammers and pullers involved to tweak the new and 50 year old stuff to work together like I wanted.
I'm sure someone that is good can do it faster, but I' slow at this stuff...
If you haven't done so already, start with new body mounts, square the cab to the frame, rebuild the door hinges (once you pop the pins out, it's just new bushings and pins), align the doors to the cab, align fenders to doors and rockers leaving them loose on the core support, (shims WILL be required), install cowl, align to doors and fenders, install hood, align hood to fenders and cowl.
Depending how things work out, you may have to go back and tweak something you aligned earlier.