Cummins big cam fuel lines size

I'm replacing all the fuel lines for this Cummins big cam. The series 60 that was in here had a number 10 fuel line and a number 6 return line.

The correct setup for the Cummins big cam is a number 10 fuel line and a number 8 return line.

I've been reading that people say a number 12 line is better because there's no restriction. Now this is a stock engine that at some point I may pull some more horsepower out of, but for now it's stock.

So here are my questions:

1) should I replace the fuel line with number 12 instead of number 10? How will that affect things? The engine has the original stock steel lines on it also.

2) if the fuel line is replaced with number 12, should the return lines get replaced with a larger number 10? Or is number eight sufficient?

3) is there enough room for me to put the dual fuel line up front without removing the fan mount?

@OLDSKOOLERnWV
@SmokinCAT