If I remember correctly the Trinity 5.8 engine uses a different crankshaft due to the differences in piston weights, so there is a difference in the counterweight to balance the rotating assembly.
Actually the Cobrajet has the GT500 crankshaft and it's interchangable between 5.4 and 5.8. The cranks that went into a Cobrajet may have had additional machining done to them, but it's not what Ford Racing repackaged and sold under their part number. I think it was a marketing ploy by Ford Racing to call their repackaged GT500 crankshaft a Cobrajet.A little off topic, but doesn't the 5.8 have the cobra jet crankshaft