Dual fuel tank confusion

[Crabass]

Currently preparing to replace the fuel pumps in my '87 short fleet dual tank Silverado. Ordered two new Bosch pumps rather than the complete pump/sending unit assembly to make sure I got Bosch pumps. Some random brain cell fired and made me realize that I'd better replace the old original sending units as well to lessen the chances of having to go through this chore again anytime soon.

BTW, for anyone that might be interested, the pump/sending units are located under the cab not the bed. Pulled the bed in order to discover this, but, fortunately, need to have the bed loose anyway to paint the bed front and cab back. Still, presumptuous, sloppy planning.
My present dilemma is making sure I get the correct sending units from a quality manufacturer without having to sell the truck to pay for 'em (can't bring myself to order the wangfoo brands from A'zon). Searching several vendors I'm seeing different descriptions which has me uncertain as to exactly what were the choices and which is correct for my rig.

Specifically, the "main/auxiliary" and "driver/passenger side" designations have me confused. I know I have the 16gal "saddle" type tanks. Just not sure if that type tank came in another size, or if the "main/aux" is the same type or perhaps some forward/rearward config. Any enlightenment would be very appreciated. Fished through five pages of search results without finding the exact info I need.