steps for assembling the front end

[Green Machine]

Hope you have new rubber cab and rad support mounts. Start with no shims under rear of cab and 1 square shim at the front. Cab has to sit square on frame and line up well with box. I have had to use an extra shim at the driver rear several times to ger the rear window line to line up with the box top edge.
Also measure the rad support side to side and get that centered, or your bumper will not center on the grill. One side or the other of the read support may need a shim to get it level.
Once everything is close, the hood becomes your alignment tool. Be prepared to loosen and re-adjust everthing many times. When you change one area, it will likey have an effect somewhere else.