Help!! Fuel Line size recommendation

[Pman1961]

I have read several posts on fuel line sizing and I am just running out of time and need to order components tonight to have my car back together for a planned cruise this coming weekend. I have mounted my dual feed line at the carburetor so that the input is located to the rear of the car. I cut the factory steel line approximately in line with the firewall and ran a braided stainless steel fuel line to the carb. The problem is the factory line measures .400 outside diameter. The 6an tube to hose fitting is made to fit on a .376 give or take outside diameter steel line. I talked with an AN manufacturer fitting rep and he stated they do not have a fitting to fit my factory steel line. He did make the suggestion since my factory steel line was thick was to try sanding the line to fit. After hours of sanding while under the car I got the fitting cap and ferrule to fit over the line. Well, when I tested the fuel line not surprisingly at all the fitting leaked. Before anyone asks the compression joint was tightened a quarter turn upon contact of the ferrule as recommended by the rep. Now my questions. I will be running a stainless braided fuel line from the pump to the carb. My current fuel line arrangement although not been driven is as follows: Factory 3/8" rubber hose from tank to 100 micron holley filter with 3/8" npt and barbed fittings, 3/8" rubber hose to Holley 12-150 150gph HP series electric pump with 3/8" npt and 3/8" barbed fittings in and out, 3/8" rubber hose to factory steel 3/8" line to firewall then 6an tube to hose fitting, summit 40 micron fuel filter, 6an steel braided hose to 6an dual feed line at carb. My engine is a 445 cu. in. KC small block dynoed at 611 hp at 5900 rpm with 750 carb. The carb was used on a 408 and felt a little weak and went to a 850 and achieved better performance. My question is since there may be a possibility of tracking my car. Should I upgrade using 1/2" or 8an fittings including the dual feed at the carb. I've done short spirited runs with no fuel starvation issues but my concern would be will the 6an line be capable of supporting longer high speed runs. I prefer to stay with the 6an as I have just purchased many new components. If the suggestion is to go to 8an has anyone experienced dropping the SPF tank and what will be required to increase the pick up line? Not afraid of fabrication. Thanks in advance!!