You might want to double check that the "return line" looking thing on that sender isn't actually a vent or a tube for a vent fitting. Having a return line dump fuel that close to the pick - up seems suspect to me, which is why I say this. It will aerate the fuel being sent and will cause stall /hesitation.
Installing a proper return line in your tank isn't a big deal either. The holley EFI master kit comes with everything you need. You just want to make sure to get any and all metal shavings that result from drilling the hole. 9/16" hole, debur, get the shavings out, install the fittings, done.
1968 Impala SS