Like Brian and I mentioned there are a ton of different applications depending on what room you have, drive line implications, bunk house/cab clearance etc.. If you’re stretching the frame then can/bunk house won’t be an issue. You more than likely be building a steerable tag tag but the search I did brought some up in it. Check out the link and look at the pics, it’ll give you a ton of ideas. Then think of what would work best for what you’re building. Then a lot of times some websites will pick them apart so you can see separate parts to better know how to fab them up.
https://www.google.com/search?q=non+lifting+tag+axle&client=safari&hl=en-us&prmd=sivn&source=lnms&tbm=isch&sa=X&ved=2ahUKEwiVhbzk1_TjAhXCW80KHYrEAOsQ_AUoAnoECA4QAg&biw=375&bih=544