Sounds like you are uncomfortable with the entire frame and want a new one.
For maybe $500 in materials you can buy all new metal, axle (made to the exact width you need), springs, coupler, etc. Then all you need is a chop saw and a welder. Network, search Craigslist, trade schools, and other sources to find a person to help. It would take a day to fabricate a new frame. For an additional $100 you can scrounge up some modern rims and good used tires.
It would be pretty easy to cut off the existing suspension and bolt on an entire new one. Here is how my suspension system is done. Spring hangers welded to angle iron and the angle iron gets bolted to the frame. Only 10 minutes of welding (easily done on a bench versus under the trailer). The only PITA is that the radius in the corner of the angle iron has to be milled out so the angle iron will fit flush against channel iron that your frame is made out of.
First though decide exactly what your objective is, detail the approximate costs and see if it's truly what you want to get involved in, and if you will end up with what you're seeking.
That's the "project manger" in me coming out, ha!
If you plan the work and work the plan anything is possible!
Cheers,
Gus
The opinions in this post are my own. My comments are directed to those that might like an alternative approach to those already espoused.There is the right way,the wrong way,the USMC way, your way, my way, and the highway.
"I'm impatient with stupidity. My people have learned to live without it." Klaatu-"The Day the Earth Stood Still"
"You can't handle the truth!"-Jack Nicholson "A Few Good Men"
"Some people spend an entire lifetime wondering if they made a difference in the world. The Marines don't have that problem"-Ronald Reagan