After a blowout I put on a stabilzer as a safety measure and also to make driving a bit more comfortable...(fewer wheel adjustments per mile). I think it is worth it for the safety and just makes a slight difference on MY RV in driving. But I don't pull a toad and I didn't have any handling issues before I installed it. It might be a bigger driving aid if you had more of a wandering chassis.
I'm not a diesel guy...but the current FR brochure lists the Legacy as a Cummins ISB 340hp engine. http://www.forestriverinc.com/brochu...cybrochure.pdf
Going to the Cummmins site...the only ISB engine is the
ISB6.7 for Motorhome (2013)
Available for: On-Highway, Motorhome
which lists a range of HP available...so I'd trust the Forest River current spec. unless you have an older brochure that says otherwise since the model # has not changed. Here's the Cummins link to that engine.
ISB6.7 for Motorhome (2013) - Cummins Engines