The later sending unit will fit the B2 tank with minimal fuss. You have a bigger problem if you are trying to use a B2 tank. It doesn't fit.
The B2 tank fits in between the frame rails, but it's much deeper than the ranger's rear tank and the filler neck is no where close to being in the right spot. If you are looking to make a twin tank Ranger early 90's E-van square tanks are a much better option. They fit funny because of depth, but the filler is in the right spot, the pump apparently works, and they are a better size.
Now if you aren't running a bed, none of that matters and you can just slap the B2 tank on there and go go go.