Stepping down fuel line size

My mechanical fuel pump to my carb both accept 5/16 line while most fuel filters and gas tanks use 3/8 line.

Would it be a problem to run 3/8 line from the tank to the fuel filter, then from the fuel filter run a 3/8 flexible hose to the fuel pump and from the fuel pump to the carb keep the 5/16?

I have a '60 Ford F100 with a straight 6 in it.

 

You are not trying to feed a couple 500-cube engines.
That's more than enough to feed a six.

 

Most V8 cars built during that same time period used 5/16" line all the way from the tank.

You'll be fine.