Anti-roll bars, helper springs original equipment

[rvplease]

I just looked at two Sunland Expresses, and one had a single pack of rear springs and no rear anti-sway bar (didn't think to look for a front one), and the other Sunland had both exra springs below the rear spring set and a rear anti-roll bar.  Was the setup without the extra springs and without the anti way bar "standard" and these two items usually optional?  If optional how important are they until I can afford them (the "standard" one has a much better coach, but needs a lot of other work).  Thanks-