a 350cid will not use more than 600cfm without forced induction, so a 750 q-jet should be fine for that 455. there was an 800cfm q-jet available in the early days that found its way onto the muscle cars. you could always have your carb bored out if you have a super high output engine and spend a lot of time at max rpm.
i ditched the original 2bbl on the 307 in my 72 burb c20 in favor of an edelbrock performer intake (idle-5500rpm) topped with an 80's q-jet. turns out i picked up one with a temp controlled accelerator pump. the temp fix was to turn it back so it runs right when fully warmed up. between that and no choke t-stat hooked up it takes a bit to get it started but it is not my daily driver and i will have the correct type of carb on there eventually.
the carb had been rebuilt recently and was on a 305 so i figured the jets were about the right size for that 307. i covered the whole setup with a dual snorkel air cleaner base from an early 70's chevy car with the big top of my dad's old 84 burb c10 350/700r with the towing package. it takes a big 14x5in air filter and will look awesome once i get it painted up in gm black. i like when i can use factory parts to hop-up a vehicle and get a custom combination that is completely bolt in and looks like it came that way.
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