You should make a steel line from pump to carb. JMO. Flexible lines between pump and carb are a leak waiting to happen which could ruin your day. I know people do it all day long without issue, but I also know people that watched the fire department hose down their flaming car because of it as well. Quality braided fuel lines are better than regular rubber ones, but I'm still not a fan.
I've honestly haven't used an aftermarket fuel pump in over 30 years. And the majority of my experience has been with Oldsmobile V8 pumps, so I'm pretty useless here. But it appears there is a seating ring missing as you point out. Did you buy it locally? If so, go back and see if they have another one you can look at and see if it has a seat ring or not. That doesn't look right to me. It appears it isn't flat across where the line attaches and seals and dips in a little. The flare nut doesn't seal anything, the line flare should, as you can see the "ring" that the piping left on the OEM pump seat ring. Does your pump have a separate fitting on it that fits in there? Usually it's a double flare fitting for the fuel line, but I'd have to examine them closer to tell. It looks like the new pump is different somehow.
I know this is probably a different pump than yours, but you can see the flare insert inside the fitting. That's usually pretty standard for outlet mechanical fuel pump and most OEM fuel filter fittings. If'n it were me, I'd take that pump back to where I bought it and start asking questions. Or look inside the box to see if there is any loose seat rings in there.
