Basically just cut at the red areas then maybe screw the flared areas down to some plywood so they are level. At same time fix where the front flares up and you can also cut the center area if you want the scoop wider. Then take some metal strips and pop rivet them to the flared parts and measure from the base of the wood to set your desired height and then pop rivet the top section in place. This should keep everything lined up.
Then after it is pieced back together take it off plywood and test fit it on hood if it fits right then lay wax paper on the backside of the scoop and back it with foam or something to keep you fiberglass patch from sagging.
then bevel each side where glass is to be done and put masking tape on the edge of these bevels to keep resin off the gelcoated areas.
once done with the scoop lay it on hood and cut hood out and bond some fiberglass strips or whatever to bottom of hood so the scoop can be fiberglassed in place. then again bevel the hood and sides of flare on the scoop and masking tape like you did on the sides. Once cured begin finishing with bondo or maybe epoxy filler.
youtube has great videos of hood scoop installs as well as smc hood repairs that might help you for the finer details of finishing.
Hope that helps