Have you measured the width on it? That is going to be the biggest pain going forward. I would recommend measuring the width on the axle you have. Pick a measurement point you like (tread center, WMS/WMS, tread outer) and decide if you want to change it. If so, which way and by how much? From there, you can downselect to axles that are reasonable for you.
WMS/WMS (wheel mounting surface) is one of the most common measurements, but you have to remove the wheels to measure it and the rim offset you use will have a significant impact on the final appearance.
What is your long term use? Is this primarily a cruiser? Hauler? Tow rig? Depending on what you are going to do with it, you might specifically want a lighter or heavier axle. Your use case will also affect what gearing you need and certain axles will only permit certain ratio ranges.
Based on some of your other posts, I assuming this was a cruiser but I realize that was an assumption.
