Rear tir rod replacement

I am at my whits end and for a simple tie rod. I can't count the number I have replaced, but this one is the worst. No matter what I try, the end just spins when trying to tighten or loosen. I have hammered it into place only to have it slide out. No amount of squeezing seems to help, even with a c clamp. I have even tried prying while loosening and it won't budge. It is only on the first few threads of the locking section. Am I using the wrong rod? Everywhere says they are all the same for all models but they are two part numbers off. Old is a 201 350 31 53 and the new is a 201 350 21 53. I am ready to take the whole rear spindle off and use an impact but I don't want to mess with the p-brake. Thanks in advance for any suggestions.
Chris
1990 300E