I think that's an "S", and not a 5 at the end of the PN in your post. Hence, 80457-S which is a a 600 cfm vac secondary with electric choke.
You'll need a 4 bbl intake... either a stock 4 bbl intake or Edelbrock Performer PN 2105. Opt for an open element air cleaner and filter.. it's a very cheap upgrade and worth a few HP, even on a 2 bbl. A 4-hole phenolic spacer is worth some low and mid-range RPM torque. To make the best of the 4 bbl induction however, consider installing headers and dual exhaust system before the carb upgrad.e
The throttle linkage may need some mods. Mine had a bell crank mounted on the intake in between two rods on either side. I had some extra Mustang parts and installed a single rod between the carb and the bellcrank mounted on the firewall.
I suggest doing a carb rebuild to establish a known good baseline.
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