I am trying to install an external fuel pump since the new block has no mechanical fuel pump provision. I am new to all this and need specific instructions regarding the wiring, specifically, the power source. Does anyone have information or diagrams? Thanks.

New pump should come with wiring instructions. Should be a simple matter of a hot-in-run source for 12v+ with an inline fuse and a ground. Wiring diags for almost all 3rd gens here to help you find a 12v+ hot-in-run to tap into:

http://www.austinthirdgen.org/index.php?pid=19