NB1 fuel rail on nb2
 

I have a nb2 miata with returnless fuel system. However, I am swapping a nb1 engine which has a return hose connected to the fuel rail. I want to know if blocking the return line work since the orginal fuel rail didn't have a return. otherwise, any suggestions since I am not planning in changing current fuel system except the fuel rail.

Put your NB2 rail on. Problem solved.