Like said, a minimum 3/8" OD(that's like a #8 AN line) inlet line with hardly any restrictions or 90° fittings. A #10 would be better and necessary in hot weather, no way around it.

The discharge don't matter. 5/16 would be plenty, plenty big enough.

And return line is really a good idea with today's blended fuel.

Why do you want electric? I have 2 cars mechanical and I just got back from beating the living hell out of my car, on the highway and on the back roads. It's like 80° here and the car did not miss a beat. I have also driven it to the top of Pikes peak(car must be tune to make that mountain) in 95° weather 2 times and in much hotter weather in Vegas and Reno. My mechanical fuel pump has never let me down. Your electric surely better be plumbed correctly if you want to run in those conditions.