I found ok not great wiring diagrams. Probably hoisted off the autozone site before AZ pulled the 3rd gen diagrams (I'm guessing copyright/payment issues).
http://www.austinthirdgen.org/index.php?pid=19
For the fuel pump IF the red wire to the relay is only hot on START, then you can use it to trigger the realy. All other wiring stays the same. Parts store relay in case of problem, and GM wiring.
I make the assumption that red wire is hot at crank only because it not it would keep the FP running all the time. I know there is a crank fuse.
Also Will, the diagram shows that pink lead from ignition switch to ign coil, so like I told you, splice that big pink out of the harness to the HEI (test it 1st, of course). S-Can that temp HEI wire you have now.