The Mercury C9, D1 and D4 scoops are externally identical, but have added studs on later versions. They were used on Cougar, Cyclone and Comet models. Originals are quite pricey, but there are a few outfits that reproduce them. Do a search for scoops for the listed models to find who is making them today and prices.
Just for reference, there are two primary versions of that scoop, though they all look the same on the outside. The C9WB is the Cougar Eliminator version, the C9GB is the Cyclone version, and the D14B and D34B are the Comet versions. The first two are identical and numbered as such. The Comet scoop is an update with more stud holes to align with the Maverick/Comet hood holes, but still interchangeable with the C9 version by moving the studs to other holes. The D1 version is molded with three part numbers and the D3 carries four. You can often use this info to get one at a better price.
If your car does not have hood stud holes, you may be able to use any version, though some cars have the reinforcement cut away at the factory to allow access for if they were there. Check you hood underside. If you see no thumb-size holes, then you'll make your own to fit whatever version you buy.
Do a search for Comet GT. Most were body color with an accent panel in front of it. This design kept it from looking so much like a stick-on scoop, like the '69 Cougars were chastised for (and why the paint style changed in '70). Note the hood panel has a large border stripe, and it goes very well with the fat 1973/4 curvy body side-stripe that accents the body lines like the yellow GT below. What changed in '73 is that the scoop is black (oddly enough - not on all GTs), but with the panel, doesn't look so out-of-place even though the hood is gloss and the scoop is satin.
Body-wise, the curvy fat stripe was most popular, with the Maverick straight wide speed-line stripe (even with the marker lights) a close second. Compare that to the blue '71 with the Eliminator-style stripe that does not follow body curves. Not popular. The Mav stripe allowed the body to establish it's own classic top-edge curve to the eye. A scoop, panel, and body stripe all in satin would also accent a difference in texture. Vinyl tops tended to hurt the lines. Food for thought.
This pic from Jay El's site is a good example of the most popular styling:
The 1971 started the style, and while the scoop was popular in body-colors, the high semi-straight side-stripe broke-up the curves - but worse, it made the car appear to be sagging in the rear:
George Melville's Maverick Grabber with Comet GT hood scoop and chin spoiler, with Grabber body-color rear body spoiler: