On my '88 B2200 I have a mechanical fuel pump located under the air cleaner, bolted onto engine on passenger side. Autozone.com shows an electrical fuel pump for your '84 B2000, and its repair guide states: "On all models through 1984, the pump is mounted on the left frame rail adjacent to the fuel tank." Look on the INSIDE of the frame rail - that's where it is on my '98 Frontier, and I had been looking on the outside of the frame rail there. Here's the picture autozone.com shows
http://www.autozone.com/N,14900078//...eResultSet.htm