Maximum AN line for NPT port size:
1/4” NPT is compatible with up to -6 AN (3/8” hard line)
3/8” NPT is compatible with up to –8 AN (1/2” hard line)
1/2” NPT is compatible with up to –10 AN (5/8” hard line)
3/4” NPT is compatible with up to -16 AN (1” hard line)
As found here:
https://www.aeromotiveinc.com/an-vs-npt/
I learned this when I was doing the fuel system on my 65. The orange and chrome Frame filter is 3/8 NPT but when I used the proper AN adapter- all my 1/2" line and fittings were appropriate.
FYI, I'm not sure I would trust that Carter pump to fuel 500hp.
This is what we are numbing on my Dad's Nova with a small block.
http://www.robbmcperformance.com/products/chevy550.html