What you need is to find a cowl from an 81+ truck, then once you set it in place you'll see where you need to drill holes. The cowls are set in to holes up by the window and screwed to the firewall at the bottom, just below the hood.
Like this
and you will need to indent the edge for the washer fluid squirter
You can see where the hole in the fender needs to be for the hood hinge.
For the most part it is a bolt on process, but there is some fab work. It's a lot easier the go from 81+ front end to 73-80 front end.