[dsraven]

best way to fit fenders is to fit the doors to the cab first. get them to fit the cab, then fit the fenders to the doors.
that said, I would still go by the original frame drawing dimensions for the front cab mounts and how they are, dimensionally, from the cab face (firewall), then get the dimension of how much gap there is under the cab to the frame, set the cab on at these dimensions and get it level with the frame, then get the rad support mounts mocked up by the original frame drawing dimensions, see how it fits with the front suspension also mocked up.
thats just me though