Hello Humble,

I too own a '91 EB 4X4 (207,000 miles and counting!)

So far I've found many of the parts I've needed at either the local discount
auto stores ( I live in Palm Bay, FL), or sometimes the local junk yards.
Recently replaced the water pump with a new one from Discount Auto; $60.
Replaced the worn nylon 4X4 hub part with a "like new" one from the local
junk yard; $50. (Ford Dealers still carry the entire hubs for several
hundred $$$)
Also bought a new exhaust from the catalytic converters back from Midas.
(don't recall the price)

I've only owned my EB for a few years, but I've found all the parts which
I've needed very easy to find.

Good luck,
Mike

Here's a couple of good sites to check out.
          http://www.explorerexpress.com/
            http://www.explorer4x4.com/

Joey