My car would hit around 4800 rpm and not rev much higher.

And it would rev higher with a bigger fuel line? No other changes? Sounds like about the time stock valve springs give up.

I can't really say about a 455 because I've never run one before but my 400 would run out of gas about the 1K foot mark with the stock single line and pump. Changed over to an elect and the problem disappeared. Electrics are noisy though.