As uts is about Impossible to find a Fuel tank for a 1989 Ranger, its the plastic type, does anyone know of a compatible tank not needed Mods to fit?

Is that frame mounted on the left side? Checkout;
http://www.lmctruck.com/icatalog/fe/t.aspx
or maybe try a search on ebay. A lot of parts aren't model/year specific, and cover a range of years.
Possibly try your dealer to get a part number that will cover a range of years, and go from there.
Or, as a last resort, junyards.
Here's a link to nation wide parts find.http://car-part.com/

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'04 Edge, Scab/flareside, 2wd, 3.0, 5 speed, 4:10 open. Billet grille, Raceline Raptor black wheels, 265/75/16 DuraTracs. Tbar crank, AAL. Fox shocks, Thrush welded SI/DO swept back side exit. Morimoto projectors, '06 tails and power mirrors. LEDs all the way around. Blacked out fender badge. Access Limited rollup tonneau. 5% tint on back three windows. Airbox mod, FWIW. And a Border Collie that likes it too!!

Found six in NC, click on the link above, and fill in the blanks.
Worth a shot.

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'04 Edge, Scab/flareside, 2wd, 3.0, 5 speed, 4:10 open. Billet grille, Raceline Raptor black wheels, 265/75/16 DuraTracs. Tbar crank, AAL. Fox shocks, Thrush welded SI/DO swept back side exit. Morimoto projectors, '06 tails and power mirrors. LEDs all the way around. Blacked out fender badge. Access Limited rollup tonneau. 5% tint on back three windows. Airbox mod, FWIW. And a Border Collie that likes it too!!

Many Thanks will give it a try
Yes mounted Left side, Plastic

Emailed a few of your suggestions. Wondering a few years ago, local guy repaired a crack in top of tank. Could it be Filler connect? As it runs down from Top of Tanks when filling, have to pump gas Real slowly?

I've found calling them works better, and telling them where you found their info. Emails are like texts to many guys, I generally don't answer either when it comes to things like this. You might have luck like that, but I wouldn't count on it.
I also tell the guys where I'm calling from, I'm a couple hundred miles from most places, or I'd showup at the counter. These guys have been boned too many times by people phishing, that they don't really think the person texting/email is actually serious. At least that's my take on it when someone chooses not to talk directly to me.
Not all the time, but frequently enough to make me do it in a more personal way.

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'04 Edge, Scab/flareside, 2wd, 3.0, 5 speed, 4:10 open. Billet grille, Raceline Raptor black wheels, 265/75/16 DuraTracs. Tbar crank, AAL. Fox shocks, Thrush welded SI/DO swept back side exit. Morimoto projectors, '06 tails and power mirrors. LEDs all the way around. Blacked out fender badge. Access Limited rollup tonneau. 5% tint on back three windows. Airbox mod, FWIW. And a Border Collie that likes it too!!