Super Springs for 2007 Born Free (has 2006 E450 chassis)

Hi,
I am looking to get Super Springs for my 2007 Born Free RV. It has a 2006 E450 Chassis. I am just not sure what Springs to purchase. When I put in year/make/model it shows the SSA47, though it looks like the SSA25 would work as well. (A retailer shows the SSA25 as the fit.) People on the Born Free owners forum say it is the SSA22, however, that spring is shown to be used with a vehicle with a top factory overload spring which my Born Free doesn’t have. Unfortunately Born Free went out of business a few years ago so I can’t ask them. Thanks