1989 Ford F150 Truck just died and now it won't start

First I need to say that this truck does not get driven very often. Never more than 2 or 3 times a month.

I was headed into town in my 89 F-150 (5.8L) when it just suddenly died on me. No sputtering, or hesitation, just on one minute and off the next.

My first assumption was that the alternator had finally died and the battery was now dead. (I've been having off and on issues with the alternator not charging the battery for months).

So I replaced the alternator with a new one (not reman or rebuilt) and put a new battery in (it had a dead cell). However, now the truck will crank but doesn't actually start.

It's got all new plugs, wires, cap, rotor, coil and relay (on the right side fender, Pos battery cable connects to it directly). Also new battery cables.

When I turn the key to ON, I can hear the relays click and then the fuel pump hums. I'm wondering if maybe the fuel pump has finally gone bad. The hum it makes sounds pretty bad (as in 60hz electricity hum). Or could it be that the pump inside the tank has gone bad?

Any ideas where to look now? My next step is a new fuel filter because that's a lot cheaper than a pump...

Thanks!
jeff