Pat,
As Dr. J. pointed out, the equalizing hitch spring bars are to transfer the
TONGUE Weight forward to equally load the front and rear axles of the tow
vehicle.
Reese shows three spring sets, for a tongue weight of 600, 800, and 1200
pounds respectively. I don't know what your tongue weight is (except a lot
less tha 1200 lbs.).
My '76 owner's manual shows factory tongue weights (without options or
variable weights) from 420 to 630 lbs for that vintage 21 -25 footers.
Newer trailers are heavier and probably have higher tongue weights too.
If you don't want to buy two sets of spring bars and the lighter tongue
weight is a little under 400 Lbs., I think you would be OK with the 600 Lb
springs. Of course your best bet would be to ask Reese the practical tongue
weight ranges for the 600 and 800 lb. springs.
Airstream or the list could give you the tongue weights of your trailers.
Actually the best way would be to simply weigh them yourself using a lever
arrangement and a bathroom scale, per the owner's manual.
Oliver Filippi