5/16 fuel line to Edelbrock AVS 2

I guess what you are asking is the thread into the carb body, looks like 5/8x20. You need an adapter from there to 5/16 inverted flare?

I see one for 3/8, not 5/16

Inverted Flare Fuel Hose Fitting #8090 For Square-Bore And ABF Carburetors

Maybe?

Rochester Carter 5/8-20 Brass Fuel Inlet Fitting 5/16" Inverted Flare | eBay