just did some testing of the mancini/carter 4845 fuel pump (supposed to be a 440hp replacement). i use a 440 block with a cam and fuel pump push rod installed and drive the camshaft bolt with a 3/8" 1200rpm drill. this pump spit out 2qts in 30 seconds but the dead head pressure was between 18-19psi. double checked the pressure with two gauges with only 1lb difference between them. i found the original carter 440hp pump from my '69 r/t and tested it . to my surprise it worked! it pumped 3+ qts in a minute and dead headed around 10psi. the mancini/carter had a 3/8" fuel inlet nipple with the 1/8" pipe threaded outlet. the stock pump has a 5/16" inlet nipple with the 1/8" outlet. it's obvious the mancini/carter (made in korea) is a no go for any stock/resto or mildly modified build without some type of serious regulator. the original pump will probably work fine in conjunction with a return line; as they were originally built.