Should I chance it?

I don't think that's correct. That would put it in the class with 4 cylinders.

That would also be a horendous ammount of power loss from all the upgrades and engineering advances done to the Mag vs the LA motors.

IIRC, the actual figure is 245, but 250 sounds much better, and is only lying a little.

Why would the industry revert back to gross HP ratings, when they have been using net since 72?

The trend lately, is actually towards "advertized" HP ratings, which seem to be just a little shy of RWHP. That's good news for us, but it's much tougher to be consistant.
Probably why they are understated.

I just have a K&N system and low restriction cat and cat back duals.

It also gets the best average MPG of any in recorded history 14-14.5, and has actually improved since it hit 110K miles (129 right now). It was geting 13.8 when I searched Dakota/Durango.com and Dakotart.com where I found several real world MPG threads.
My ball joints aren't bad, neither my windshield, nor my a/c leak, and the trans has never been repaired or replaced (all common issues with Dakotas of this vintage).