fuel sending unit advice

can someone point me in the right direction in looking for a fuel sending unit 1/2 inch fuel pickup and a 3/8 return for a 70 duster. I was going to soldier a return in my own but it is stainless steel it dosent soldier well

I haven't seen a 1/2" with a 3/8" return line but there are 1/2" with no return lines available. Could it be the return line is on one of the tank ports?