[eschaider]

I think it would be easier for you and probably less expensive to just buy an FFR car (if that's what you want) in some state of disrepair, with the expectation that the disrepair will only need a manageable level of TLC. The job would probably be quicker, easier, and less expensive.

If you were a fabricator, chances are you would not be asking the questions you are. That means your fabrication skills toolbox is essentially bereft of experience and skills. This is a very big warning flag. You might do well to pay attention to it.