I have a 1998 Mazda B4000 pickup and the computer in it has gone bad and no replacement part is made any more?

Affected by this are the power windows, wipers and the 4 wheel drive. Don't care about the windows but wondering if there's way to re-wire the wipers and the 4 wheel drive to bypass the computer. The Mazda B4000 is really a Ford Ranger, checked with Ford for the computer and not made any more. Doesn't seem right that parts aren't available for this vehicle, so many cars and trucks are lasting longer now, you would think that they would stock parts. Does anyone have a suggestion as to whether the wipers/4wheel drive can bypass the computer. Thanks in advance to anyone who might be able to help me.

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