I have a very similar 455 setup to yours but running a stock-style Airtex 40710 big bowl pump with a vapor return (listed for early 70's 400/455s). I installed a new tank and the new stock-style 3/8" pickup is plumbed through the original 3/8" tubing to the pump. I figured it would be enough but now not so sure.
I am about 800 miles into the engine since the initial break in and so still tuning, but have come a long way with it. The shift point feels "right" around 4800 RPM or so but this is just at the ragged edge of fuel delivery. Sometimes it pulls through the shift just fine and sometimes it bogs right at or just after the shift. Also I sometimes get a bit of vapor lock on hot days so having a return line isn't an instant cure in itself.
I am thinking about trying a Robmc pump, but if the original 3/8" fuel tubing is the problem (either restricted somewhere or just too small) then a better pump probably won't solve my problem. I don't want to go electric- been there, done that. It works but at a cost- noise, etc.
Just some food for thought...
Walt
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1969 Lemans vert, matador red, 462 CI, 3.07 12-bolt posi
1974 455 TA, admiralty blue/red interior HPP "cover car" - sold
"The best way to show a car is to drive it"
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