well it does make 20-40 extra ft-lbs than the 4.0 v6, so a stock ranger auto trans should handle it, as far as hp the 4bt makes just over 100.
But if you are concerned about the 4bt tearing up the stock ranger auto trans then you could try a small vw diesel or get a c4 transmission for your 4bt.

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Beaten up '05 Ford Ranger XL 3.0

MODS-Alpine CDA-105 head unit, throttle cable mod, painted rims, pooleo's camo painted bezel and mustang dome, fold-a-cover