That's the widest two row core I've ever seen. Here's something you may try. I did this on Vixen. I got probably 10-15 degrees out of it. I made some baffles out of plastic corrugated sign material to fill in the spaces on either side between the back of the grille and front of the core support. This forces more air through the radiator. I plan on filling in some of the spaces between the back of the valance and the K frame underneath, too. My car doesn't run hot, but I prefer it to run as cool as possible. Anything you can do to force more air through the grille will help.
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