I really doubt there was much thought about gap size when these trucks were made.
To adjust the hood from top to bottom ( hood to cowl or hood to doghouse { your second picture}) raise the front of the cab and rear of the doghouse this will align the hood sides and even out the gaps. Start at the cab and move forward.
The support bars under the hood locate the doghouse at the correct angle to the cab and the correct length from the cab. It's a cat and mouse chase to get both right while getting the gaps rights. Then you need to be sure the cab is pointing straight ahead so the left matches the right, same with the doghouse, there is a lot of wiggle room at the hold down bolts.
To open or close the gaps, slide the cab forward or the doghouse back towards the cab to get the gaps where you want them.
Just remember to have good welting under the hood, as these old trucks flex a lot and the hood is always moving around.
