Is the main fuel pump relay working or maybe stuck? When you turn ignition key to on, does the fuel pump run for a few seconds? If not, I'd pull out the relay, pop the cover and make sure no solder joints are cracked. Does the 91 have a crank position sensor? If so this would be at the back of the engine, it attached to a flimsy bracket at the bell housing, these can act sporadic or die. Either of these can shut you down completely, it will crank all day, but never start. I am assuming you have fuel with your new pumps.