[dsraven]

Looks great.
On your door issue, check the dimension of your step and get that right first. Then fit the door to the cab with no latch in place, so the latch doesnt have to bring the door to its final height, then install the latch and adjust. When the door fits the cab then fit the fender to the door. Use shims under the front cab mounts and rad support to get things right. Also, some guys have had to move the cab around to get the gaps right. Use the drivers side front cab mount as a pivot as it (originally) was a smaller hole than the rest for this purpose. That rotational movement of the cab can help get the fender to door gaps the same as well as the hood fitment.
If you google 55-59 chev assembly manual you should find a site to download a digital copy. This will have some body dimensions so you can get the step dimension correct. There is another site on moving the cab to get the gaps correct