I went through this when I modified my trailer (pictures in photo album). I don't remember part numbers, etc., but I know that finding springs seemed more complex than necessary to get the right part, but then I was also changing the axle.
A couple of the things that I would look into while it is apart: Is your tongue weight correct? Now is the chance to move the axle forward/back a little to improve handling. Second, look into plastic spacers that go in between the springs. Some require a hole to be drilled in the spring, and that is no fun even with a drill press (I had to use a concrete bit). Other spacer types secure differently. The spacers eliminate the "sticktion" that occurs between leaves as the springs rust. Makes a noticeable difference. As do my shock absorbers, but that was mainly for remote gravel road travel.
I got my axle through Fisheries Supply. Springs were local. Fisheries had a deal where you could order the part through their regular truck delivery and not pay shipping. You just had to wait for Fisheries to put in their next order from that vendor. It took me a month to get the axle, but it ended up being half price by not paying shipping.
