I'd work through Titsy's list, as if an engine has spark, fuel, timing and compression, it has to run....
I think you can safely rule out compression, as loosing compression to all eight cylinders at once is beyond unlikely, and at this mileage wear is not an issue, so its likely to be fuel timing or ignition. on a V8 poor compression is normally either one or two cylinders (head gasket) or mega high miles. a V8 will start happily on 6 cylinders, so this is very unlikely.
low fuel pressure would likely cause at least a cough, as there is nothing happening at all, there is either no fuel pressure (pump?) or the injectors are not firing. as you say you can hear the pump prime, non firing injectors are on the hit list. there should be a schrader valve on the rail, even if you don't have a pressure gauge, you can do a basic check by pressing the core of valve in, if the fuel is at full pressure it should squirt as opposed to dribble out. (be careful, its probably about 30 - 40 PSI)
the other option is of course no spark, or timing completely out (crank trigger failure?), but in either situation I'd expect to be able to smell fuel through the exhaust after prolonged cranking.
I'd definitely be leaning toward the injectors not firing.....
you can often hear the injectors tick as they fire too, have a listen while someone else cranks it, if all is quiet there may be a clue there..
